Question 1

Q1: State whether the following statements are True or False. (i) We can only see that part of the Moon which reflects sunlight towards us. (ii) The shado...

Accepted Answer

(i) True Reason: The Moon does not produce its own light. It shines by reflecting sunlight. From Earth, we can only see the portion of the Moon's surface that is illuminated by the Sun and is facing us. (ii) False Reason: The phases of the Moon are caused by the changing viewing angle of the Moon's...

Question 2

Q10: If we stopped having leap years, in approximately how many years would the Indian Independence day happen in winter?

Accepted Answer

Given: - Indian Independence Day: August 15th (summer/monsoon season). - Winter season in India is roughly from December to February. - A calendar year without leap years = 365 days. - A tropical year (the time for seasons to repeat) is approximately 365.25 days. To Find: The approximate number of y...

Question 3

Q11: What is the purpose of launching artificial satellites?

Accepted Answer

Artificial satellites are human-made objects launched into orbit around the Earth (or other celestial bodies) to serve various important purposes. According to the chapter, these purposes include:    Communication: Relaying telephone calls, television broadcasts, and internet data across large dista...

Question 4

Q12: On which periodic phenomenon are the following measures of time based: (i) day (ii) month (iii) year?

Accepted Answer

The basic units of time in our calendars are based on the following natural periodic phenomena: (i) Day: The concept of a day is based on the rotation of the Earth on its own axis. The solar day, which is approximately 24 hours, is the average time it takes for the Sun to appear in the same position...

Question 5

Q2: Amol was born on 6th of May on a full Moon day. Does his birthday fall on the full Moon day every year? Explain your answer.

Accepted Answer

Answer: No, Amol's birthday will not fall on a full Moon day every year. Explanation: This is due to the difference in the lengths of a solar year and a lunar year. 1.  Solar Year: A birthday, like May 6th, is based on the solar calendar (Gregorian calendar), which is approximately 365.25 days long....

Question 6

Q3: Name two things that are incorrect in Fig. 11.10.

Accepted Answer

The figure described shows a star positioned inside the horns of a crescent Moon, within the unlit portion of the lunar disk. Here are two things that are incorrect about such a depiction: 1.  A Star Cannot Be Seen Through the Moon: The Moon is a solid, opaque celestial body. A star is a distant obj...

Question 7

Q4: Look at the pictures of the Moon in Fig. 11.11, and answer the following questions. (i) Write the correct panel number corresponding to the phases of...

Accepted Answer

The panels are described as follows: A: A fully illuminated Moon. B: A waning gibbous Moon (most of the left side is lit). C: A third-quarter Moon (left half is lit). D: A waning crescent Moon (a sliver on the left is lit). E: A completely dark disk. F: A waxing crescent Moon with earthshine (faint...

Question 8

Q5: Malini saw the Moon overhead in the sky at sunset. (i) Draw the phase of the Moon that Malini saw. (ii) Is the Moon in the waxing or the waning phase?

Accepted Answer

(i) Phase of the Moon: The phase Malini saw is the First Quarter Moon. This is depicted as a circle with its right half illuminated and its left half dark. (ii) Waxing or Waning Phase: The Moon is in the waxing phase. Explanation: The position of the Moon in the sky relative to the Sun helps determi...

Question 9

Q6: Ravi said, "I saw a crescent Moon, and it was rising in the East, when the Sun was setting." Kaushalya said, "Once I saw the gibbous Moon during the a...

Accepted Answer

Answer: Kaushalya is telling the truth. Explanation:    Ravi's statement is incorrect.        A crescent Moon is always positioned relatively close to the Sun in the sky.        At sunset, the Sun is in the West. A waxing crescent would be visible in the western sky shortly after sunset, and it woul...

Question 10

Q7: Scientific studies show that the Moon is getting farther away from the Earth and slower in its revolution. Will luni-solar calendars need an intercala...

Accepted Answer

Answer: Luni-solar calendars will need an intercalary month less often. Explanation: 1.  Purpose of Intercalary Month: Luni-solar calendars add an extra month (intercalary month or Adhika Maasa) periodically to reconcile the shorter lunar year (about 354 days) with the longer solar year (about 365 d...

Question 11

Q8: A total of 37 full Moons happen during 3 years in a solar calendar. Show that at least two of the 37 full moons must happen during the same month of t...

Accepted Answer

To Show: At least one month in a 3-year period must contain two full moons. Proof using the Pigeonhole Principle: 1.  Identify the 'Pigeons': The 'pigeons' are the individual events we are distributing. In this case, the pigeons are the 37 full Moons.        Number of pigeons = 37. 2.  Identify the...

Question 12

Q9: On a particular night, Vaishali saw the Moon in the sky from sunset to sunrise. What phase of the Moon would she have noticed?

Accepted Answer

Answer: Vaishali would have noticed the Full Moon. Explanation: For the Moon to be visible in the sky for the entire duration of the night (from sunset until sunrise), it must rise in the East at approximately the same time the Sun sets in the West, and it must set in the West at approximately the s...

Picture label (e.g. A, B, C, etc.)	Phase of Moon
	Three days after New Moon
	Full Moon
	Three days after Full Moon
	A week after Full Moon
	Day of New Moon

NCERT Solutions