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Q1. Assertion (A): The phases of the Moon are caused by the Earth's shadow falling on the Moon.
Reason (R): The Earth's shadow on the Moon causes a lunar eclipse.
Choose the correct option
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Q2. Assertion (A): Lunar and solar eclipses do not occur every month.
Reason (R): The Moon's orbit around the Earth is slightly tilted with respect to the Earth's orbit around the Sun.
Choose the correct option
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Q3. Ravi says: 'I saw a crescent Moon, and it was rising in the East, when the Sun was setting.' Kaushalya says: 'Once I saw the gibbous Moon during the afternoon in the East.' Who is telling the truth?
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Q4. In a solar calendar, a total of 37 full Moons occur during 3 years. Three years contain 3 × 12 = 36 months. What does this imply?
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Q5. On a particular night, Vaishali saw the Moon in the sky from sunset to sunrise. Which phase of the Moon must she have observed?
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Q6. If we stopped having leap years, in approximately how many years would Indian Independence Day (15 August, currently in monsoon / summer) drift into winter?
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Q7. Assertion (A): If the Moon's revolution around the Earth slowly becomes slower with time, luni-solar calendars will need to add the intercalary month less often, not more often.
Reason (R): A slower Moon means a longer lunar month, so 12 lunar months get closer in length to a solar year, reducing the gap that the intercalary month is meant to fix.
Choose the correct option
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Q8. Read the three statements about the Moon and identify the correct ones:
I. Only one half of the Moon always faces the Earth.
II. The illuminated half of the Moon is always the one that faces the Sun.
III. On a new Moon day, the illuminated half of the Moon faces the Earth, but we cannot see it.
Which statements are correct?
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Q9. Assertion (A): It takes a long time before differences between a calendar based on the tropical year and one based on the sidereal year become noticeable.
Reason (R): The sidereal year is longer than the tropical year by only about 20 minutes.
Choose the correct option
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Q10. About the Surya Siddhanta and the Indian tracking of solstices, consider the three statements:
I. The Surya Siddhanta noted that the pattern of stars called Makar (Capricorn) would be in the background of the Sun around the winter solstice in those ancient times.
II. Indian astronomers tracked equinoxes and solstices by identifying the stars that rose at sunset.
III. The Taittiriya Samhita verse 6.5.3 also records the Sun's six-month motion southwards and six-month motion northwards.
Which statements are correct?
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Q11. Consider the following statements about the Indian National Calendar:
I. The Calendar Reform Committee was set up in 1952 by the Government of India.
II. The Unified National Calendar was adopted from 21 March 1956 CE, which is 1 Chaitra 1878 Saka.
III. The Indian National Calendar follows the general principles of the Surya Siddhanta.
Which statements are correct?
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Q12. Makar Sankranti is based on a sidereal calendar and shifts ahead in the tropical (Gregorian) calendar by one day every 71 years. By approximately how many days will it have shifted in 710 years?
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Q13. In Activity 11.1, a student begins observing at sunrise on the day after a full Moon and continues for 15 days. From day 2 onwards, how should the bright portion of the Moon change from the previous day, and how should the Moon's position with respect to the Sun appear?
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Q14. Assertion (A): The shadow of a vertical stick is shortest at the moment when the Sun is at its highest position in the sky.
Reason (R): The natural cycle of the Sun reaching its highest position in the sky each day is what defines a day.
Choose the correct option
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Q15. Read the three statements about luni-solar calendars used in India:
I. They primarily use the Moon's phases for counting days and months.
II. They make adjustments to stay in step with the cycle of seasons.
III. They never add an extra month, because that would make the year too long.
Which statements are correct?
