Chapter 2 - The Sun, the Moon and the Earth
Q. 1. Correct the wrong statements. Write down the corrected ones.
(1) The moon revolves around the sun.
Ans: Wrong
Correct statement: The moon revolves around the earth.
(2) On a full moon day, the moon, the sun and the earth are positioned in this sequence.
Ans: Wrong
Correct statement: On a full moon day, the sun, the earth, and the moon are positioned in this sequence.
(3) The revolutionary orbits of the earth and the moon are in the same plane.
Ans: Wrong
Correct statement: The revolutionary orbits of the earth and the moon are not in the same plane, but they make an angle of 5 degrees with each other.
(4) In one revolution of the moon, its orbit intersects the earth’s orbit only once.
Ans: Wrong
Correct statement: In one revolution of the moon, its orbit intersects the earth’s orbit twice.
(5) It is alright to observe a solar eclipse without protecting the eyes.
Ans: Wrong
Correct statement: It is harmful to observe a solar eclipse without protecting the eyes.
(6) An annular solar eclipse occurs when the moon is in the perigee position.
Ans: Wrong
Correct statement: An annular solar eclipse occurs when the moon is in its apogee position.
Q. 2. Select the correct option.
(1) Solar eclipse
Ans: Option (b)
(2) The shape of the sun disc at the time of the annular solar eclipse.
Ans: Option (b)
(3) Apogee position of the moon.
Ans: Option (a)
3. Complete the following table.
| Details | Lunar Eclipse | Solar Eclipse |
|---|---|---|
Phase of the moon | __________ | New moon day |
Sequence | Moon-Earth-Sun | __________ |
Type of eclipse | __________ | __________ |
Maximum duration of total eclipse | 107 minutes | __________ |
Ans:
| Details | Lunar Eclipse | Solar Eclipse |
|---|---|---|
Phase of the moon | Full moon day | New moon day |
Sequence | Moon-Earth-Sun | Sun-Moon-Earth |
Type of eclipse | Total lunar eclipse & Partial lunar eclipse | Total solar eclipse, Partial solar eclipse and annular solar eclipse |
Maximum duration of total eclipse | 107 minutes | 7 minutes and 20 seconds |
4. Draw and label the diagrams.
(1) Total and partial solar eclipse.
Ans:
(2) Total and partial lunar eclipse.
Ans:
5. Answer the following.
(1) Why do the sun, the moon and the earth not lie in one and the same line on every full moon and new moon day?
Ans:
(i) The orbital paths of the earth and the moon are not in the same plane.
(ii) The moon’s revolutionary orbit makes an angle of about 5⁰ with that of the earth.
(iii) As a result, the moon intersects the plane of the earth’s orbit twice during one revolution.
(iv) On each new moon day, the lines joining the earth, the sun, and the moon make an angle of 0⁰ whereas on each full moon day, this angle is of 180⁰.
(v) Therefore, the Sun, the moon, and the earth do not lie in one and the same line on every full moon and new moon day.
(2) When a total solar eclipse occurs, why is a partial eclipse also seen from the earth?
Ans:
(i) If the moon is between the sun and the earth, the shadow of the moon falls on the earth.
(ii) This shadow is of two types: the central portion of the shadow is darker and the periphery is lighter.
(iii) In the area of dark shadow on the earth, the sun becomes completely invisible. This condition is known as a total solar eclipse.
(iv) However, during the same period, at the places where the shadow is lighter, the sun disc appears partially covered. This condition is described as a partial solar eclipse.
(3) Suggest measures that can be taken to eradicate the superstitions related to the eclipses.
Ans: The following measures can be taken to eradicate the superstitions related to the eclipse:
(i) With various activities and demonstrations given in the textbook, we can explain the fact that an eclipse is just a result of the sun, the earth, and the moon being in specific positions, and there is nothing ‘auspicious’ or ‘inauspicious’ about it.
(ii) We can collect scientific information about eclipses by referring to books and the internet and sharing the same by way of posters, charts, group discussion, street play, etc.
(4) What precautions should we take while observing a solar eclipse?
Ans: While observing a solar eclipse, it is necessary to view the sun’s disc through dark glasses or special goggles made for that purpose; otherwise, the intense light of the sun can be harmful to the naked eye.
(5) What types of solar eclipses will occur in perigee conditions?
Ans: A total solar eclipse and a partial solar eclipse will occur in perigee conditions.