STD 6 Basic Science: Chapter 08 Moon and Stars - Questions and Answers | Teaching Manual


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Chapter 08: Moon and Stars - Questions and Answers 
1. Does light fall everywhere on the earth at the same time?
Answer: Only one half of the earth receives light at the same time.

2. What causes days and nights?
Answer: It is due to the earth's rotation that day and night continuously appear.

3. When you turn the globe to the left, in which direction is its rotation? 
* From east to  west
* From west to east
Answer: From west to east

4. Let’s do an activity.
Materials required: Model of the earth (globe), a steel rod and an arrangement for lighting a bulb (Textbook Page: 100)
Activity
Remove the globe’s stand.  Arrange the bulb and the globe as shown in the figure. The north pole of the globe should be towards the north. Light the bulb after ensuring maximum darkness in the classroom. The bulb is used in place of the sun. Imagine that the globe is the earth. Now observe the globe from the side of its north pole. Don’t you see light in the portion facing the sun and darkness on the other side? Gently turn the globe to the left. Now, don’t you see that the dark portion entering into the lighted area and the lighted area moving into the dark area?
Answer: Only one half of the earth receives light at the same time. The earth spins from west to east. It is due to the earth's rotation that day and night continuously appear.

5. Activity
* Locate our approximate position in the globe.
* On that area, fix a pin in the east-west direction using cello tape.
* Fix a small red colour bindi at the top end, a white one in the middle and green at the bottom.
* Imagine that you are on the white bindi. Now the bindis at the ends are in your east and west.
i. What is the colour of the bindi on the east?
Answer: Red
ii. What about the colour of the one in the west?
Answer: Green
iii. Light the bulb and gently turn it to the left.
Observe the positions of the white bindi when there is sunrise, noon and sunset. On the basis of your findings complete the following table
6. Mark positions A, B and C on the globe, as shown in the figure. Make models of children using Thermocol and fix them in these positions. Which are the east and the west of each child?
Answer: For all children, the area towards the position of A is East and the area towards the position of C is west.
i. On the basis of the observations, complete the following table:
ii. What are the inferences you arrive at by analysing the table?
Answer: The position of the sun does not change. In fact, it is due to the rotation of the earth, the sun appears in the east in the morning, above the head at noon and in the west in the evening.

7. Given below are the positions of the moon at the time of sunset observed by Appu on three different days.
i. Is there a change in the position of the moon?
Answer: Yes, there is a change in the position of the moon
ii. In which direction does the change of position take place?
Answer: West- East
iii. What is the reason for the change in position of the moon?
Answer: The position of the moon appears to change because of the revolution of the moon around the earth.

8. How long does the moon's revolution take?
Answer: The moon completes one revolution around the earth in 27 ⅓ days.

9. Try out the following activity.
Materials required: Five yellow plastic smiley balls, five glass cups, five stools and an emergency lamp.
Activity
Draw a semicircle on the floor of the classroom in an east-west direction. Arrange the stools, the cups and the balls in five equidistant positions as shown in the figure. The smiling face of all the balls should face the centre of the circle. Light the emergency lamp and place it on the west side in such a way that the light falls on the balls. As far as possible, prevent the light from the outside from entering the classroom by closing doors and windows. From the centre of the circle, observe all the five balls.
* The smiling face of the ball placed in which position is completely exposed to light?
Answer: Ball at 5
* The smiling face of the ball placed in which position is not exposed to any light at all?
Answer: Ball at 1
* The smiling face of the ball placed in which position is partially lit by the light?
Answer: Ball at 3

10. Observe the figure.
Different positions of the moon in its path of revolution around the earth are depicted here.
* Is it possible to see the moon when it reaches the position marked 1? Why?
Answer: We can't see the moon when it reaches the position marked 1. Because the part of the moon which faces Earth didn't receive sunlight.
* What change occurs in the appearance of the moon when it comes to the position marked 2?
Answer: At the position marked 2 we can see the moon in the shape of a crescent.
* In which position do you see the full moon?
Answer: At position marked 5
* In which position do you see the half-moon?
Answer: At the position marked 3
* Analyse the figure and match the facts given below by drawing lines:

* Repeat the above experiment by bringing slight changes. Change the
semicircle drawn on the ground into a full circle. Place the balls in positions
2, 3 and 4 in their corresponding positions on the other semicircle. The smiling
face should face the centre of the circle. Switch on the emergency lamp. Standing at the centre of the circle, observe the balls in the order from 5 to 1. 
Write down your findings in the science diary.
Answer: From this experiment, we can understand that from the new moon day to the full moon day, the lighted portion of the moon becomes more visible and from the full moon day to the new moon day, there is a decrease in the visibility of the lighted area of the moon from the earth.

11. What is waxing?
Answer: From the new moon day to the full moon day, the lighted portion of the moon becomes more visible. This is called waxing.

12. What is called waning?
Answer: From the full moon day to the new moon day, there is a decrease in the visibility of the lighted area of the moon from the earth. This is called waning.

13. Why the moon always faces the Earth same side?
Answer: The moon completes a revolution around the earth in 27% days. It takes the same time to complete one rotation as well. That is why only one face of the moon appears in the direction of the earth always.

14. Do you see only the moon in the sky at night? What are the other things you see?
Answer: 
* The Moon
* stars

15. Are they all of the same colour? What are the colours of the stars you see?
Answer: The stars show a multitude of colours, including red, orange, yellow, white, and blue.

16. In which shape do we draw a full moon?
Answer: We will draw a full moon in a spherical shape.

17. If so, don’t you think the sun and stars should be drawn in the Same Shape?
Answer: The sun and stars are spherical in shape.

18. Why do stars twinkle? Explain.
Answer: Stars are self-luminous celestial bodies. The rays of light from the stars undergo a continuous change in their direction while traversing through various layers in the atmosphere. This is why Stars appear to twinkle.

19. Which star is the nearest to the earth?
Answer: Sun

20. How big does the sun appear to us? Is the sun bigger than the Earth?
Answer: The sun appears like a small sphere from the earth. But, the Sun is bigger than the Earth. The sun is a star that can hold about 12 lakh earth within it.

21. The size of stars is something beyond our imagination. Despite being so big, why do the stars appear small in size?
Answer: The size of stars is something beyond our imagination. Despite being so big, the stars appear small in size. Because the further away an object is, the smaller it appears, even if it is very big. For example, Most of the aeroplanes you see usually carry on board a large number of people. But when they go up a few kilometres, they appeared to be diminished in size.

22. How would you distinguish the stars from one another, all of which look alike?
Answer: We can distinguish them by grouping them into different shapes and patterns.

23. A) Try joining the dots from 1 to 7 continuously.
B) What shape do you get?
Answer: We got the shape of a spoon.
C) What is the name given by westerners to this constellation?
Answer: ‘big dipper'
D) What is the name given by Indians to this constellation?
Answer: Saptnharshis.

24. We can see the big dipper in the sky. When and where?
Answer: We see them in the northern sky in the evening, in the summer season. In the months of December and January, they are seen at midnight.

25. What are constellations?
Answer: Constellations are groups of stars, imagined into shapes by joining them together using lines.

26. Orion consolation is used by the people in past. For what it was used?
Answer: This is the constellation used by people in the past to ascertain direction while travelling in deserts and the sea.

27. We can see the Orion constellation from Earth. When?
Answer: This constellation can be seen after dusk in the months of January, February and March

28. The line joining the head and the sword of Orion (hunter) reaches the ...........
Answer: polar star.

29. Cassiopia is seen in the sky. When?
Answer: Cassiopia is seen in the sky in the evening from October to December

30. Observe this constellation.
A) What is the name of this constellation?
Answer: scorpius (vrischikam)
B) This constellation is seen in months of ............ and .............
Answer: August and September

Let us Assess

1. Is it in Gujarat or Assam that the sunrise is seen first? Why?
Answer: Assam. Due to the rotation of Earth from east to west, the region in almost East will see the sunrise first. Assam is the state in the East. So, it will receive the sunlight first.

2. If the moon does not rotate along with its revolution, will it be possible to see all parts of the moon from the earth? Justify your answer.
Answer: No, we cant see all the parts of the moon from the Earth, if the moon does not rotate along with its revolution. If the moon does not rotate on its own axis, we can see only one part of the moon. Because the moon rotates around the earth in an orbit that is not changing.

3. Prepare a questionnaire for conducting a quiz programme on astronomy in such a way that the following are the answers.
a) Sun
b) Constellations
c) Alpha Centauri
d) Saptharshis
e) Full moon
f) Thiruvathira
g) Rotation of the earth
h) 27⅓ days
Answer:
a) Which star is the nearest to the earth?
b) What is the name of groups of stars, imagined into shapes by joining them together using lines?
c) Which is the second nearest star to the earth?
d) In what name the big dipper constellation is known in India?
e) What is the name of the moon in which the whole of the lighted portion of it faces the earth?
f) Give an example for the stars which are greater than the sun?
g) What causes days and nights?
h) How many days does the Moon take to complete one rotation around its axis?












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