Question

The light from the sun takes 500s to reach the earth. Assuming that the speed of light is 3,00,000km/s, calculate the distance between the sun and the earth.
(A) 100 million km
(B) 150 million km
(C) 200 million km
(D) 300 million km

Answer 1

Hint From the speed formula$speed = \dfrac{{dis\tan ce}}{{time}}$. Distance is the product of speed and time taken. Substitute the values of speed and time to get the distance travelled.

Complete step-by-step answer
As we know, that speed of a body is the distance covered by it in unit time interval.
So,
$speed = \dfrac{{dis\tan ce}}{{time}}$
$dis\tan ce{\text{ }} = {\text{ }}speed{\text{ }} \times {\text{ }}time$
$\Rightarrow dis\tan ce{\text{ }} = {\text{ }}300000{\text{ }} \times {\text{ }}500$
$\Rightarrow dis\tan ce{\text{ }} = {\text{ }}1.5{\text{ }} \times {\text{ }}{10^8}$
$\Rightarrow dis\tan ce{\text{ }} = {\text{ }}150{\text{ }}million{\text{ }}km$

Therefore the correct answer is option B

Note The distance between Earth and the Sun is not constant throughout the year, it depends greatly on the time of the year. This is because the orbit of the Earth is slightly oval. So there is a period when the Earth is closer to the Sun while there is some other time when the Earth is slightly farther away. But since we need to calculate the distance with the help of the given information we ignore this slight deviation from the circular orbit.