202110242-TRIUMPH-STUDENT-WORKBOOK-PHYSICAL_SCIENCE-G08-PART2

Physical Science Workbook_8_P_2.pdf 1 11/5/19 6:22 PM Name: ___________________________________ Section: ________________ Roll No.: _________ School: __________________________________

Table of Contents 1 30 10 SOME NATURAL PHENOMENA 66 11 STARS AND THE SOLAR SYSTEM 106 12 GRAPHS OF MOTION PROJECT BASED QUESTIONS TABLE OF CONTENTS

10. SOME NATURAL PHENOMENA SESSION 1 LIGHTNING - CAUSES, CHARGE, AND PROTECTION 1.1 Mind Map 1. Lightning SESSION 1. LIGHTNING - CAUSES, CHARGE, AND PROTECTION 1

2. Charge 1.2 Terminology i. Discharge – To relieve of a charge Or Electric discharge describes any flow of electric charge through a gas, liquid or solid. ii. Lightning –Lightning is defined as a flash of light that is caused by the discharge of electricity in the atmosphere. iii. Lightning conductor – A metal rod or wire fixed to an exposed part of a building or other tall structure to divert lightning harmlessly into the ground. iv. Crust – The outer layer of the Earth, between the surface and the mantle, which is up to 40 miles deep. v. Electroscope – An electroscope is an early scientific instrument that is used to detect the presence and magnitude of electric charge on a body. 1.3 Key Concepts i. Lightning is caused due to the electric discharge between the earth and clouds or in between different clouds. ii. Lightning conductors are used to protect buildings. SESSION 1. LIGHTNING - CAUSES, CHARGE, AND PROTECTION 2

iii. The flow of charges through a conductor is called electric current. iv. Some objects can be charged by rubbing with other materials. v. Static electricity consists of charges that cannot flow. vi. Charges are of two types: positive and negative. vii. Like charges repel each other and unlike charges attract each other. viii. An electroscope is used to detect whether a body is charged or not. ix. Earthing is the process of transfer of a charge from a charged object to the earth. 1.4 Reflection on Concepts Q1. [AS1] Which places are not safe during thunderstorm? [Refer to TB page 145 Q2] A. The following places should be avoided during thunderstorm – i. Travelling in an open place. ii. Standing under tall trees in open fields or in a garden/ park. iii. Staying in multi–storied buildings which do not have lightning conductors. iv. Standing near electric poles or telephone poles. Q2. [AS5] Describe with the help of a diagram an instrument which can be used to detect a charged body. [Refer to TB page 145 Q1] A. The instrument that can be used to test whether an object is carrying charge or not is electroscope. Description of electroscope: SESSION 1. LIGHTNING - CAUSES, CHARGE, AND PROTECTION 3

Take an empty jam bottle. Take a piece of cardboard slightly bigger in size than the mouth of the bottle. Pierce a hole in it so that a metal paper clip could be inserted. Open out paper clip as shown in the figure. Cut two strips of aluminium foil about 4 cm×1 cm each and hang them on the paper clip. Insert the paper clip having the strips of aluminium foil in to the cardboard lid so that it is perpendicular to it as shown in the figure. This entire device works as an electroscope. Procedure to detect a charged body by using an electroscope: Charge a refill and make it touch the end of the paper clip. The aluminium foil repel each other because the strips of aluminium foil receive the same charge from the charged refill through the paper clip. The strips carrying similar charges repel each other and hence they move apart. This proves electroscope is useful in detecting a charged body. 1.5 Application of Concepts Q1. [AS1] Sometime a cracking sound is heard while taking off our sweater during winters. Explain. [Refer to TB page 145 Q1] A. Woollen sweater gets charged due to friction with the body. When it is taken off, due to collision of charges a cracking sound is heard. Q2. [AS1] Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by a charged balloon? [Refer to TB page 145 Q4] A. A balloon when charged acquires a particular type of charge. As both charged balloons are charged by the same process, both acquire same type of charge. Like charges repel each other and thus the two balloons repel each other. When an uncharged balloon is brought near to a charged balloon the uncharged body acrquires opposite charge by the process of induction and thus gets attracted to the charged balloon. Q3. [AS1] Give two examples of effects in your daily life which are caused by transfer of charges. [Refer to TB page 145 Q2] SESSION 1. LIGHTNING - CAUSES, CHARGE, AND PROTECTION 4

A. i. Sparks on electric pole when wires become loose or when wind blows and shakes the wires. ii. Earthing is provided in buildings to protect us from electrical shocks that may be caused due to any leakage of charge. iii. A lightning conductor provides an easy route for the transfer of electrical charge. Q4. [AS3] Inflate two balloons and rub both of them with a cloth first and then with different material. Will they attract each other in both cases? [Refer to TB page 145 Q3] A. If two inflated balloons are rubbed with cloth, they get same charge and repel each other. If two inflated balloons rubbed with different material, they may get opposite charge and attract each other. 1.6 Higher Order Thinking Skills Q1. [AS2] We know that clouds have charges. Can we produce current through these charges? [Refer to TB page 145 Q3] A. No we can not produce current through these charges. Since the late 1980s, there have been several attempts to investigate the possibility of “harvesting lightning energy”.A thundercloud is a immense storehouse of energy. If we can find some way to store the energy, we may be able to solve the problem of producing electricity from cloud charge. Lot of research is going on in this area. Q2. [AS6] How do you appreciate the efforts of the scientists to develop a Lightening con- ductor to protect buildings from the effect of lightening? [Refer to TB page 145 Q4] A. The lightning rod, which Benjamin Franklin invented in 1749, is a metal pole mounted atop a building that draws lightning’s electrical charge away from the structure. The rod is attached to an aluminium or copper cable that’s connected to an underground conductive grid. This allows the electricity to dissipate harmlessly. Because lightning tends to strike the tallest object in the vicinity, lightning rods must be taller than any buildings or other objects in the area. If installed properly, a lightning rod will carry a lightning bolt’s electrical charge through a path of least resistance along the cable in to the ground, reducing the risk of fire or heat damage from the strike. SESSION 1. LIGHTNING - CAUSES, CHARGE, AND PROTECTION 5

Q3. [AS7] The weather department has predicted that a thunderstorm is likely to occur on a certain day. Suppose you have to go out on that day, would you carry an umbrella? Explain. [Refer to TB page 145 Q1] A. No, we should not carry an umbrella in a thunderstorm. During thunderstorms, electrical discharge from clouds can travel through the metallic rod of the umbrella. This may give an electrical shock to the person who is carrying it. Hence it is not safe to carry an umbrella during lightning. 1.7 Suggested Experiments Q1. [AS3] Conduct an experiment to find the effects of charged bodies which have been rubbed by different materials. [Refer to TB page 146 Q1] A. Aim: To find the effects of charged bodies which have been rubbed by different materials. Materials required: A ball pen refill, a balloon, a comb, an eraser, a steel spoon, polythene sheet, plain paper, woollen cloth etc. Procedure: i. Rub the above objects against materials listed in the following table. ii. In each case, bring the rubbed object near small pieces of paper and note whether they attract pieces of paper or not. iii. Record your observation in a table by writing ’YES’ or ‘NO’. SESSION 1. LIGHTNING - CAUSES, CHARGE, AND PROTECTION 6

Object Material used for Whether paper Refill testing pieces are Plain paper attracted? Polythene sheet No Yes Woollen cloth Yes Inflated balloon Dry hair Yes Polythene sheet Yes Woollen cloth Yes Object Material used for Whether paper Comb testing pieces are Eraser Plain paper attracted? Steel spoon Polythene sheet No Woollen cloth Dry hair Yes Polythene sheet Woollen cloth Yes Plain paper Polythene sheet No Woollen cloth No No No No No SESSION 1. LIGHTNING - CAUSES, CHARGE, AND PROTECTION 7

Conclusion : Some objects like refill, comb, etc. when rubbed with some specific materials are able to attract light objects like bits of paper. But some objects like steel spoon donot attract pieces of paper even after rubbing. Q2. [AS3] Conduct an experiment to findout the presence of charge on a body. [Refer to TB page 146 Q2] A. Materials Required: Thermocol ball, silver foil, thread, stand. Procedure: i. Make a small ball from a thermocol sheet. Wrap this in thin silver foil to cover them. ii. Suspend it to a stand with the help of a thread. iii. Bring a glass rod rubbed with a silk cloth near the suspended ball. iv. The thermocol ball gets attracted towards the glass rod. v. Now touch the silver foil on the thermocol ball with charged glass rod. vi. Remove the glass rod from the ball and again rub it with the silk cloth and bring it close to the suspended ball. vii. The thermocol ball moves away from the glass rod. viii. Therefore, to test if a body is charged or not bring near a positively charged body and a negatively charged body, one by one. Observations: i. When a charged body (glass rod rubbed with silk cloth) is brought near an uncharged body(thermocol) it induces an opposite charge in it and hence gets attracted to the glass rod. ii. In the second case we have charged the thermocol ball by touching it with a charged glass rod. When we brought the glass rod near the ball, as both of them have similar charge the ball gets repelled by the glass rod. SESSION 1. LIGHTNING - CAUSES, CHARGE, AND PROTECTION 8

Conclusion: From the above experiment we can conclude that attraction is not a sure test to know the presence of charge, but repulsion is. Objective Questions (1) Which of the following cannot be charged easily by friction? (Pg 146;TB Q 1) (A) A plastic scale (B) A copper rod (C)A wollen cloth (D)Piece of wood Correct Answer: B (2) When a glass rod is rubbed with a piece of silk cloth (Pg 146;TB Q 2) (A) Rod and cloth acquire positive charge (B) Rod becomes positively charged while the cloth has a negatively charged (C)Rod and the cloth both acquire negative charge (D)Rod becomes negatively charged while the cloth has a positively charged Correct Answer: B (3) It can protects buildings from the effects of lightning –(Pg 146;TB Q 5) (A) Seismograph (B) Seismoscope (C)Gold leaf electroscope (D)Lightning conductors Correct Answer: D SESSION 1. LIGHTNING - CAUSES, CHARGE, AND PROTECTION 9

SESSION 2 EARTHQUAKE - CAUSES AND PROTECTION 2.1 Mind Map 1. Earthquake SESSION 2. EARTHQUAKE - CAUSES AND PROTECTION 10

2. Protection against earthquakes 2.2 Terminology i. Earthquake – A sudden movement of the earth’s crust caused by the release of stress accumulated along geologic faults or by volcanic activity. Also called seism, temblor. ii. Earth’s plates – Earth’s lithosphere is divided into large rigid blocks (plates) that are floating on semifluid rock and are thus able to interact with each other at their bound- aries. iii. Richter scale – The Richter scale is used for measuring the magnitude of earth- quakes. iv. Seismograph – An instrument that measures and records details of earthquakes, such as force and duration. v. Seismoscope – An instrument for recording only the time or fact of occurrence of earthquakes. SESSION 2. EARTHQUAKE - CAUSES AND PROTECTION 11

2.3 Key Concepts i. An earthquake is caused due to the adjustments of the outer most layers of the earth’s plates. ii. Earthquake tends to occur at the boundaries of earth’s surface known as seismic or faulty zones. iii. Intensity of earthquake is measured by Richter scale. iv. An earthquake is a sudden shaking or trembling of the earth. v. It is not possible to predict the occurrence of an earthquake. vi. Earthquakes tend to occur at the boundaries of earth’s plates. These boundaries are known as fault zones. vii. Destructive energy of an earthquake is measured on the Richter scale. The earth- quake measuring 7 or more on Richter scale can cause severe damage to life and property. viii. We should take necessary precautions to protect ourselves from earthquakes. 2.4 Reflection on Concepts Q1. [AS1] List three states in India where earthquakes are more likely to occur. [Refer to TB page 145 Q3] A. Gujarat, Assam and Jammu and Kashmir. Q2. [AS1] Explain how you determine the intensity of earthquake. [Refer to TB page 145 Q4] A. The tremors produce waves on the surface of the earth. These are called seismic waves. The waves are recorded by an instrument called the seismograph.This instru- ment records the seismic waves on a paper which moves under it. By studying these waves, scientists can construct a complete map of the earthquake. Intensity of an earth- quake is measured by Richter scale.There is another method of measuring the intensity of an earthquake using the moment magnitude scale which is based on the amount of displacement that occurred along a fault zone rather than the measurement of ground motion at a given point.The moment magnitude measures energy released by the earth- quake more accurately than the Richter scale. It is the only magnitude scale that ade- quately measures the size of large earthquakes. SESSION 2. EARTHQUAKE - CAUSES AND PROTECTION 12

Q3. [AS7] Suppose you are outside your house and earthquake occurs. What precautions would you take to protect yourself? [Refer to TB page 145 Q5] A. According to me following precautions should be followed: i. Try to find an open place away from tall buildings, tall trees, electrical poles etc. ii. If travelling in a bus or car then do not come out when an earthquake strikes. Ask the driver to drive to an open field. 2.5 Application of Concepts Q1. [AS6] How would you appreciate the efforts of scientists to develop an instrument to assess the intensity and source of earthquake? [Refer to TB page 145 Q5] A. The efforts of scientists to develop an instrument to assess the intensity and source of an earthquake is thoroughly appreciated because they provide an assessment of earthquake and what are the rescue measurements to be taken by the government, private organizations and also provide preventative measurements that would be taken when earthquake occurs. So these scientists providing life for people and services are thoroughly appreciated. 2.6 Higher Order Thinking Skills Q1. [AS2] Is there any alternative method to find the intensity of the earthquake? [Refer to TB page 145 Q2] A. There is another method of measuring the intensity of an earthquake using the moment magnitude scale which is based on the amount of displacement that occurred along a fault zone rather than the measurement of ground motion at a given point.The moment magnitude measures energy released by the earthquake more accurately than the Richter scale. It is the only magnitude scale that adequately measures the size of large earthquakes. 2.7 Suggested Projects Q1. [AS4] Which country in the world is frequently affected by earthquakes? Collect the information and photographs on the recently occurred earthquake in Japan. [Refer to TB page 146 Q1] A. Japan is frequently affected by earthquakes. Students’ activity. SESSION 2. EARTHQUAKE - CAUSES AND PROTECTION 13

Q2. [AS4] Find out if there is any organisation in your area which provides relief to those suffering from natural disasters. Enquire about the type of help they render to the earth- quake victims. Prepare a brief report on the problems of earthquake victims. [Refer to TB page 146 Q2] A. Students’ activity. Relief organisations provide food, water, shelter and first aid to earthquake victims. They also make lists of the refugees at different camps so that locating the loved one of a victim becomes easier. Earthquake causes: i. Damage to human made structures. ii. Damage to towns and cities. iii. Devastating fires. iv. Loss of human and animal life. v. Spread of diseases. Q3. [AS4] Collect amounts of the devastation caused by a tsunami in India from your parents, friends and neighbourhood and write a report. [Refer to TB page 146 Q3] A. Students’ activity. Objective Questions (1) The destructive earthquakes have magnitudes higher than on the Richter cy- cle.(Pg 146;TB Q 3) (A) 3.0 (B) 4.0 (C) 7.0 (D) 2.0 Correct Answer: C (2) The instrument is called to approximately measure the intensity of earthquake is (Pg 146;TB Q 4) (A) Seismograph (B) Seismoscope (C)Gold leaf electroscope (D)Lightning conductors Correct Answer: A SESSION 2. EARTHQUAKE - CAUSES AND PROTECTION 14

—— CCE Based Practice Questions —— AS1-Conceptual Understanding Very Short Answer Type Questions 1. State true or false. [Refer to Session 10.1] (i) We must take shelter under a tall tree during a thunderstorm. [ ] (ii) Electrical appliances like T.V and computers must not be used during a thunderstorm. [] (iii) During a thunderstorm if one is travelling outside in a car they must close the doors and windows of the car and stay inside. [] 2. Match the following. [(Session 10.1)] [] Column B Column A a. Repel i. Electric spark ii. Copper [ ] b. Current iii. Like charges [ ] c. Attract iv. Unlike charges [ ] d. Lightning v. Moving charges [ ] e. Good conductor 3. Fill in the blanks. [Refer to Session 10.1 ] (i) A metallic rod, taller than the building is installed in the walls of the building during its construction to protect it from . (ii) We must not travel in an during a thunderstorm. CHAPTER 10. SOME NATURAL PHENOMENA 15

4. State true or false. [] [Refer to Session 10.2 ] (i) Natural phenomena can be predicted to some extent. 5. Answer the following questions in one sentence. [Refer to Session 10.2 ] (i) What are seismic zones? (ii) How is moment magnitude scale more accurate than Richter scale? (iii) Who are seismologists? 16 CHAPTER 10. SOME NATURAL PHENOMENA

(iv) Name two devices used to measure earthquakes. (v) What are seismic waves? (vi) What is a seismograph? 17 (vii) What is a seismoscope? CHAPTER 10. SOME NATURAL PHENOMENA

6. Fill in the blanks. [Refer to Session 10.2 ] (i) The magnitude of an earthquake is expressed in terms of . (ii) A thunderstorm is accompanied by . (iii) Most of the destructive earthquakes have a magnitude higher than . (iv) are the only natural phenomena whose occurrence cannot be predicted. (v) The outer most layer of the earth is made of fragments called . (vi) Unlike many other scales, Richter scale is not . (vii) Zones which are more prone to earthquakes are called . (viii) The instrument other than seismograph which can be used to measure the intensity of an earthquake is called . Short Answer Type Questions 7. Answer the following questions in 3-4 sentences. (i) [(Session 10.1)] What is an electroscope? CHAPTER 10. SOME NATURAL PHENOMENA 18

(ii) [(Session 10.1)] What is earthing? 8. Answer the following questions in 3-4 sentences. (i) [(Session 10.2)] Define an earthquake. (ii) [(Session 10.2)] How is an earthquake caused? 19 CHAPTER 10. SOME NATURAL PHENOMENA

Long Answer Type Questions 9. Answer the following questions in 6-8 sentences. (i) [(Session 10.1)] Where must one take shelter during a thunderstorm? (ii) [(Session 10.1)] What is that one must not do during a thunderstorm? CHAPTER 10. SOME NATURAL PHENOMENA 20

10. Answer the following questions in 6-8 sentences. (i) [(Session 10.2)] Mention a few safety measures that need to be taken during an earth- quake. CHAPTER 10. SOME NATURAL PHENOMENA 21

AS2-Asking questions and making hypothesis Short Answer Type Questions 11. Answer the following questions in 3-4 sentences. (i) [(Session 10.1)] Rakesh says it is important to install a lightning conductors on the tall buildings. Why does he say so? AS3-Experimentation and field investigation Long Answer Type Questions 12. Answer the following questions in 6-8 sentences. (i) [(Session 10.1)] Write an experiment to prove that a glass rod rubbed with silk cloth contains charge. CHAPTER 10. SOME NATURAL PHENOMENA 22

AS4-Information skills and projects Long Answer Type Questions 13. Answer the following questions in 6-8 sentences. (i) [(Session 10.2)] Which regions in Andhra Pradesh are more prone to earthquakes? Collect pictures and information about the earthquakes which have occurred in Andhra Pradesh. AS5-Communication through drawing and model making 23 Long Answer Type Questions CHAPTER 10. SOME NATURAL PHENOMENA

14. Answer the following question. (i) [(Session 10.1)] Draw a diagram to show what would happen when two balloons which are hung from threads and kept close to each other acquire: a) similar charges. b) different charges. CHAPTER 10. SOME NATURAL PHENOMENA 24

(ii) [(Session 10.1)] Draw a diagram of a lightning conductor and show how the charge flows to the ground during a lightning strike. AS6-Appreciation and aesthetic sense, Values Long Answer Type Questions 15. Answer the following questions in 6-8 sentences. (i) [(Session 10.2)] Express your feelings on the following topic: Loss incurred to biodiversity by earthquakes. CHAPTER 10. SOME NATURAL PHENOMENA 25

AS7-Application to daily life, concern to bio diversity Short Answer Type Questions 16. Answer the following questions in 3-4 sentences. (i) [(Session 10.1)] Why is earthing done? (ii) [(Session 10.1)] What is a lightning conductor? CHAPTER 10. SOME NATURAL PHENOMENA 26

Long Answer Type Questions 17. Answer the following questions in 6-8 sentences. (i) [(Session 10.1)] On your street you see a very tall building, but it does not have any protection against lightning. What would you suggest the owner of the building to do and why? 18. Answer the following questions in 6-8 sentences. (i) [(Session 10.2)] You and your family are in the midst of an earthquake. What are the measures you would take to protect your family and yourself? CHAPTER 10. SOME NATURAL PHENOMENA 27

Objective Questions AS1-Conceptual Understanding 19. Choose the correct answer. (i) Two objects which have like charges will always (A) attract each other (B) repel each other (C)either attract or repel (D)neither attract nor repel (ii) The charge acquired by a glass rod when it is rubbed with silk is considered as (A) neutral (B) negative (C)either positive or negative (D) positive (iii) The process of transferring charge from a charged body to earth is called (A) earthing (B) processing (C) transferring (D) charging (iv) Earthquake is caused due to the following reason: (A) Series of large waves from the ocean (B) Strong winds on the earth’s surface (C)Electric discharge between clouds and the earth (D)Disturbance deep inside the earth’s crust CHAPTER 10. SOME NATURAL PHENOMENA 28

AS3-Experimentation and field investigation 20. Choose the correct answer. (i) Which of the following cannot be charged by friction, if held by hand? (A) A plastic scale (B) A copper rod (C)An inflated balloon (D)A woollen cloth AS4-Information skills and projects 21. Choose the correct answer. (i) Which of the following is not a safety measure to be followed during a lightning? (A) Taking shelter under a short tree instead of a tall tree (B) Close the windows and doors if you are travelling in a car or bus (C)Stand near electric poles or telephone poles (D)Stay in a multi storied building only if it has a lightning conductor (ii) Name the scientist who showed that lightning and the spark from clothes are essentially the same phenomena. (A) Thomas Alva Edison (B) Franklin D. Roosevelt (C)Benjamin Franklin (D)Isaac Newton (iii) Magnitude of an earthquake is measured using the following scale: (A) Celsius (B) Pascal (C) Richter (D) Kelvin AS6-Appreciation and aesthetic sense, Values 22. Choose the correct answer. (i) Which device is used to measure the occurrence or the time of occurrence of an earthquake? (A) Lightning conductor (B) Seismograph (C) Barometer (D) Seismoscope (ii) A device which can be used to test whether an object is carrying charge or not is called (A) Telescope (B) Electroscope (C) Periscope (D) Microscope CHAPTER 10. SOME NATURAL PHENOMENA 29

11. STARS AND THE SOLAR SYSTEM SESSION 1 INTRODUCTION AND MOVEMENTS OF SUN 1.1 Mind Map SESSION 1. INTRODUCTION AND MOVEMENTS OF SUN 30

1.2 Terminology i. Meridian – An imaginary great circle on the earth’s surface passing through the North and South geographic poles. ii. Shadow – A dark figure or image cast on the ground or other surface by a body intercepting light. iii. Dakshinayanam – When the sun looks like it is like traveling towards the south of the sky, it is called the dakshinayanam. iv. Uttarayanam – When the sun looks like it is like traveling towards the north of the sky, it is called the uttarayanam. v. Hemisphere –A half of the earth, usually as divided into northern and southern halves by the equator, or into western and eastern halves by an imaginary line passing through the poles. 1.3 Key Concepts i. We observe different objects in the sky. ii. The objects which are found in the sky are known as celestial objects. iii. We get light from the Sun. iv. Shadows form when objects obstruct the path of the light ray. v. The shortest shadow cast by a vertical object on the ground always falls in the north–south direction. vi. Movement of earth around the sun causes change in seasons. 1.4 Application of Concepts Q1. [AS1] How does day and night occur? [Refer to TB page 169 Q8] A. Due to rotation of earth around its imaginary axis, day and night occur. The portion of earth facing the sun at any time experiences day and the portion facing away experi- ences night. Q2. [AS3] How can you find out north–south direction at your place? [Refer to TB page 169 Q2] A. The sun seems to rise in the east and sets in the west. If you face towards the sun in the morning, the left hand side is north and the right hand side is south. 1.5 Higher Order Thinking Skills Q1. [AS2] Even though we do not have clock, we can know the time by observing some shadows in day time. Think and discuss with your friends how can we know the time at night. [Refer to TB page 169 Q1] A. We can find out the time in the night by tracing the location of moon and locations of SESSION 1. INTRODUCTION AND MOVEMENTS OF SUN 31

other constellations. 1.6 Suggested Experiments Q1. [AS3] Conduct an experiment to find out the local noon time of your village/ town. [Refer to TB page 170 Q1] A. The shortest shadow cast by a vertical object on the ground always falls in the north–south direction. You can use this fact to locate directions. The time when the shortest shadow occurs is called the local noon time at that place. Q2. [AS3] Conduct an experiment to make a sun–dial. [Refer to TB page 170 Q2] A. Take a cardboard and cut a right angled triangle ABC from it. Angle C of the trian- gle should be equal to the latitude of your place and angle A should be 90°. i. Fix the cardboard triangle vertically in the middle of the rectangular wooden box. Glue strips of the paper along the edges of BC and the wooden board and make the triangle stand erect. ii. Place the wooden board with the triangle on level ground in an open space which gets sunlight throughout the day. Base BC of the triangle should be placed in north– south direction with B pointing on the earth. iii. At nine in the morning, draw a line along the shadow of side AC on the wooden board. Write the time alongside the line. Draw lines of the shadow of side AC at one hour intervals (use a clock to check the time) through the day till sunset and mark the time for each line. Your sun–dial is ready. 1.7 Suggested Projects Q1. [AS4] What is the duration of day and night today? Collect the information about the duration of day and night for past 7 days from the newspaper, analyse it and say whether summer or winter is going to come?( [Refer to TB page 170 Q3] A. Students’ activity. SESSION 1. INTRODUCTION AND MOVEMENTS OF SUN 32

SESSION 2 PHASES OF THE MOON AND ECLIPSES 2.1 Mind Map 1. Solar Eclipse SESSION 2. PHASES OF THE MOON AND ECLIPSES 33

2. Lunar Eclipse 3. Phases of Moon – SESSION 2. PHASES OF THE MOON AND ECLIPSES 34

3. Phases of Moon SESSION 2. PHASES OF THE MOON AND ECLIPSES 35

2.2 Terminology i. Moon – The natural satellite of the earth, visible (chiefly at night) by reflected light from the sun. ii. Phases – Any stage in a series of events or in a process of development . iii. Total Solar Eclipse – An eclipse of the sun in which the moon completely hides the solar surface or photosphere and thereby cuts off all direct rays of sunlight from the observer. iv. Total Lunar Eclipse – An eclipse in which the moon is completely immersed in the umbra of the earth’s shadow. 2.3 Key Concepts i. Changes in appearance of moon are called phases of moon. ii. Moon has no atmosphere like on the earth. iii. Solar eclipse occurs when the moon obstructs the view of the sun on the earth. iv. Solar eclipses occur only on New moon days. v. Lunar eclipse occurs when the moon is obstructed by the sun. vi. Lunar eclipses occur only on Full moon days. SESSION 2. PHASES OF THE MOON AND ECLIPSES 36

2.4 Application of Concepts Q1. [AS2] What are the questions that tease your mind while looking at the sky? [Refer to TB page 169 Q5] A. i. How many stars are there in the sky? ii. Where are they going? iii. What is the distance between those stars? iv. How can we measure the distances? v. Why the Pole Star is not moving? vi. What are the streaks of light seen occasionally? vii. Is the distance between all the stars same? Q2. [AS5] Draw different phases of moon and arrange them from full moon day to new moon day. [Refer to TB page 169 Q4] A. SESSION 2. PHASES OF THE MOON AND ECLIPSES 37

Objective Questions (1) When the moon completely covers the sun as seen from the earth is known as –( (Pg 169; TB Q 1) (A) Partial solar eclipse (B) Total solar eclipse (C)Annular eclipse (D)Hybrid eclipse Correct Answer: B (2) Moon is to the earth. (Pg 170; TB Q 4) (A) Natural satellite (B) Artificial satellite (C) Comet (D) Astroid Correct Answer: A SESSION 2. PHASES OF THE MOON AND ECLIPSES 38

SESSION 3 STARS, SOLAR SYSTEM AND SATELLITES 3.1 Mind Map 1. Solar system 2. Stars – 39 SESSION 3. STARS, SOLAR SYSTEM AND SATELLITES

2. Stars 3.2 Terminology i. Solar system – A solar system is the collection of planets, asteroids, and moons (moons orbit the planets) that occupy a space around a sun and are held within the gravitational pull of the Sun. Our solar system consists of eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune) and a planetoid, Pluto. ii. Stars – Any of the celestial bodies visible at night from Earth as relatively stationary, usually twinkling points of light. iii. Constellations – An easily recognized group of stars that appear to be located close together in the sky and that form a picture if lines connecting them are imagined. iv. Satellite – A celestial body orbiting around a planet or star. v. Comet – A comet is an icy small Solar System body that, when passing close to the Sun, heats up and begins to outgas, displaying a visible atmosphere or comma, and sometimes also a tail. vi. Meteor – A small body of matter from outer space that enters the earth’s atmosphere, becoming incandescent as a result of friction and appearing as a streak of light. SESSION 3. STARS, SOLAR SYSTEM AND SATELLITES 40

vii. Meteorite – A piece of rock or metal that has fallen to the earth’s surface from outer space as a meteor. viii. Asteroid – A small rocky body orbiting the sun.They are sometimes called minor planets. 3.3 Key Concepts i. Pole Star is situated in direction of the earth’s axis. ii. We can find satellites, constellations, asteroids, meteors, meteorites and comets in the space. iii. Artificial satellites provide useful information. iv. Aryabhatta was the first Indian artificial satellite. 3.4 Reflection on Concepts Q1. [AS1] Why does the Pole Star seem to be stationary? [Refer to TB page 168 Q1] A. The pole star is situated in the direction of the earth’s axis and that is why it does not appear to move even though all stars appear to be moving because of the rotation of the earth. The Pole Star lies on the line of the imaginary axis of earth’s rotation. So it seems to be stationary. Q2. [AS1] How many planets are there in the solar system? What are they? [Refer to TB page 168 Q2] A. There are 8 planets in our solar system. They are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Q3. [AS1] Among all the planets what is the special thing about earth? [Refer to TB page 168 Q3] A. Earth is the only planet in the solar system where life exists. Q4. [AS1] How did people come to an understanding that earth is spherical? [Refer to TB page 168 Q4] A. In olden days people felt that earth was flat because it looked flat. However they had a doubt as to how the water in oceans remained there, why it did not spill out of the earth. To get clarity they assumed a fencing around the flat earth. After that SESSION 3. STARS, SOLAR SYSTEM AND SATELLITES 41

1) They assumed the shape of earth as round by observing the shadow of earth in lunar eclipse. In every eclipse they found the shape of earth is in round even though there is a chance of getting linear, elliptical shadows by a circular object. 2) Some sailors, who started their journey in ocean, reached the same place af- ter traveling large distance in one direction only. 3) Observing ships approaching the port also helped to change their opinion about the shape of the earth, that is, usually they see smoke of the ship first and then the top of the ship after that the whole ship. 4) Observations about the movement of stars and different stars visible from different places on the earth also helped to think about the shape of the earth. Through all such observations made by so many people at so many places on the earth they came to an understanding that earth is spherical. And then it is get clarified in 1969 when man landed on the moon and observed the earth’s shape from the moon. Q5. [AS1] How did people come to an understanding that earth rotates on its own axis? [Re- fer to TB page 168 Q5] A. People from olden days thought that earth is located in the center of the universe with sun, moon and stars moving around it. They also thought that sun, moon and stars are located on transparent concentric spheres surrounding the earth, because they are not falling down. The three spheres are rotating on their axis from east to west that is why sun, moon and stars appear to revolve from east to west around the earth. They also assumed that the sphere on which sun is located rotates east to west and oscillates from south to north that is why uttarayanam and dakshinayanam are happening. Because of the uneven movement of some stars (actually they are planets) which they observed, it became very difficult to explain the model of universe which required so many transparent spheres around the earth. Nicholas Copernicus suggested that the sun is at the center of the universe and all other celestial objects are revolving around the sun. Then how do day and nights occur. It was assumed that earth rotates on its axis. This model could explain the occurrence of day and night. In this way people came to an understanding that earth rotates on its axis. SESSION 3. STARS, SOLAR SYSTEM AND SATELLITES 42

3.5 Application of Concepts Q1. [AS1] Is it possible to see the Pole Star for people who live in the southern hemisphere of the earth? Why? [Refer to TB page 169 Q3] A. The Pole Star is not visible from southern hemisphere because it is situated on the North pole of the imaginary axis of the earth. Q2. [AS1] What factors to be taken into consideration to view the polestar at your place? [Refer to TB page 169 Q1] A. We can locate the pole star ( Polaris ) with the help of two constellations namely Great Bear and Cassiopeia. We can easily recognize the great bear with its rectangular head in the northern sky. Cassiopeia is there in the same part of the sky, its six stars forming the letter ‘M’. If we are able to spot only the great bear, we have to look at the two stars that form the outer side of its rectangular head. Then we have to extend an imaginary line from these two stars (as shown in given figure). The pole star will be located on that extended line with a distance of about 5 times the distance between these two stars. Q3. [AS3] What are the planets that you have seen in the sky? When do you observe those planets? [Refer to TB page 169 Q6] A. Mercury, Venus, Mars and Jupiter. SESSION 3. STARS, SOLAR SYSTEM AND SATELLITES 43

i. Mercury can be observed just before the sun rise or just after the sunset near the horizon. ii. Mars can easily be seen from Earth with the naked eye. It is seen as a reddish object in the sky. iii. Venus is the planet which is bright enough to be seen in a mid–day clear sky and the planet is easy to see when the Sun is low on the horizon. iv. Jupiter can be seen near the moon. It can be seen as a very bright object for about half the year in the evening sky. Q4. [AS7] What is the use of artificial satellites in our life? [Refer to TB page 169 Q7] A. Use of artificial satellites – i. Provide telecommunication. ii. Help in remote sensing. iii. Identify minerals and metal deposits. iv. Help in weather forecasting. v. They are used for transmitting television and radio signal. 3.6 Higher Order Thinking Skills Q1. [AS6] How do you appreciate the construction of knowledge about the universe by our ancestors? [Refer to TB page 169 Q3] A. i. In olden days people observed the shadows to calculate the time. ii. They understood that day and night are formed due to rotation of the earth. iii. Sailors sailing boats in night time observed the Pole Star and other constellations to determine their time and location. Q2. [AS7] We launched many artificial satellites around our earth for different purposes. What do you think about the impact of artificial satellites and their radiation on biodiver- sity? [Refer to TB page 169 Q2] A. Though we are having so many uses of artificial satellites, there are also some limitations. Non–functional satellites, blasted rocket parts etc. revolve around the earth as garbage. SESSION 3. STARS, SOLAR SYSTEM AND SATELLITES 44

Due to satellites,radiations are released into the atmosphere which affects human DNA. Some species are badly affected due to cell phone radiations (e.g –Bees and Sparrows) and pollute the atmosphere causing greenhouse effect. Q3. [AS7] Among 8 planets of our Solar system, Earth is the only planet supporting life. Explain how we should protect our earth and its environment? [Refer to TB page 169 Q4] A. If we pollute the environment, the temperature rises. If the soil is polluted, yielding of the crops decreases and food problem arises. If the atmosphere is polluted due to industries and CFCs, the ozone layer may get depleted which is protecting us from UV rays coming from the sun.We must take special care to protect our environment so that life on earth is not disturbed. There are little things we can do every day to help reduce greenhouse gases and make a less harmful impact on the environment. Taking care of the Earth is not just a respon- sibility ––it’s a privilege.We can protect our earth and its environment by initiating the following steps – 1. Planting trees and reducing industrial pollution. 2. Save water. 3. Save electricity. 4. Increase the use of renewable energy. 5. Raise awareness of and build the capacity to adapt to climate change. 6. Reduce, recycle and reuse. 3.7 Suggested Projects Q1. [AS4] Collect information about cosmic dust( wastage) from newspapers, internet and make a poster on your school panel board about the consequences of cosmic dust. [Refer to TB page 170 Q2] A. Students’ Activity. SESSION 3. STARS, SOLAR SYSTEM AND SATELLITES 45

Cosmic dust consists of microscopic particles of solid materials floating in space be- tween stars. The materials that make cosmic dust are silicates, graphite, hydrocarbons and oxides. These are also found on earth, where they can be classified as pollutants. However they are not harmful in the interstellar space. Cosmic dust plays an important role in cosmology. Metals from the cosmic dust play a part in various phenomena that affect our climate. Student may refer the following web link – http://goo.gl/yuA4lV Q2. [AS4] Collect the information what the Chandrayaan –I brought the information from the moon through the news papers, magazines. [Refer to TB page 170 Q1] A. Students’ activity. Objective Questions (1) The planet which is near to the earth is –(Pg 169;TB Q 2) (A) Mercury (B) Venus (C) Jupiter (D) Saturn Correct Answer: B (2) The brightest planet among all the planets –(Pg 170:TB Q 3) (A) Mercury (B) Venus (C) Jupiter (D) Saturn Correct Answer: B (3) was the first Indian Artificial satellite. (Pg 170: TB Q 5) (A) Insat (B) Kalpana –I (C) Aryabhatta (D) EDUSAT Correct Answer: C SESSION 3. STARS, SOLAR SYSTEM AND SATELLITES 46

—— CCE Based Practice Questions —— AS1-Conceptual Understanding Very Short Answer Type Questions 1. State true or false. [Refer to Session 11.1 ] (i) When the sun looks like it is travelling towards the south of the sky, it is called ‘dakshi- nayanam’. [] (ii) Sundial is based on the magnetic field of the Earth. [] (iii) The length of a shadow changes from morning to evening. [ ] 2. Answer the following questions in one sentence. [Refer to Session 11.1 ] (i) What is a sundial? (ii) What are the celestial objects that we can see in the sky? CHAPTER 11. STARS AND THE SOLAR SYSTEM 47

3. State true or false. [Refer to Session 11.2 ] (i) A total lunar eclipse occurs when the earth’s shadow obscures all of the moon’s visible surface. [] (ii) The moon’s surface is barren and dusty. [] 4. Answer the following questions in one sentence. [Refer to Session 11.2 ] (i) Write one objective of Chandrayaan –1. 5. State true or false. [] [Refer to Session 11.3 ] [] [] (i) Mercury is the brightest planet. [] (ii) Jupiter is the largest planet. (iii) Mars is called as the red planet. 48 (iv) Venus is the smallest planet. CHAPTER 11. STARS AND THE SOLAR SYSTEM