Approximately how long does sunlight take to reach the Earth?
- A.8 minutes 20 seconds
- B.1.3 seconds
- C.4.2 years
- D.24 hours
Correct answer
Explanation
The correct answer is A, 8 minutes 20 seconds. The Sun is about 149.6 million kilometres from the Earth, a distance called one astronomical unit, and light travels about three lakh kilometres in a second. Dividing one by the other gives roughly 500 seconds, that is eight minutes and twenty seconds, so we always see the Sun as it was a little over eight minutes ago.
Option B, 1.3 seconds, is the time moonlight takes to reach us from a distance of about 384,400 kilometres, and examiners often place the two figures in the same question. Option C, 4.2 years, is the time light takes from Proxima Centauri, the nearest star after the Sun. Option D, 24 hours, is the time the Earth takes for one rotation on its axis and has nothing to do with the travel of light.
Read the full article: Solar System and the Earth: Planets, Moon and Motions
Practice Questions
View allWhich is the hottest planet of the solar system?
- A.Mercury
- B.Venus
- C.Mars
- D.Jupiter
Show answer
Venus is wrapped in a very thick atmosphere of carbon dioxide, which lets sunlight in but does not let the heat escape.
Read the full explanation →Which is the largest planet of the solar system?
- A.Saturn
- B.Neptune
- C.Jupiter
- D.Uranus
Show answer
Jupiter is the fifth planet from the Sun and the largest of all by both diameter and mass; it is a gas giant of hydrogen and helium.
Read the full explanation →Apart from Uranus, which planet rotates on its axis from east to west, that is in a direction opposite to most planets?
- A.Mercury
- B.Venus
- C.Mars
- D.Saturn
Show answer
Almost every planet, the Earth included, rotates from west to east, which is why the Sun appears to rise in the east.
Read the full explanation →The occurrence of seasons on the Earth is caused mainly by which of the following?
- A.The changing distance between the Earth and the Sun
- B.The rotation of the Earth on its axis
- C.The tilt of the Earth's axis along with its revolution around the Sun
- D.The gravitational pull of the Moon
Show answer
The axis of the Earth is tilted about 23.5 degrees from the vertical and keeps pointing in the same direction throughout the year.
Read the full explanation →Which planet has the lowest density, so low that it would float if placed in a large enough body of water?
- A.Jupiter
- B.Saturn
- C.Neptune
- D.Mercury
Show answer
Saturn is a huge ball of hydrogen and helium spread over an enormous volume, and its average density is less than that of water.
Read the full explanation →