Question

It takes time 8min for light to reach from the sun to the earth surface. If speed of light is taken to be 3×10^8ms^-1, find the distance from the sun to the earth in km. ​

Answer 1

Explanation:

Distance =speed *time

Time =8*60s

=3*10^8*8*60= 1.44*10^11 m

Answer 2

Given :

▪ Time taken by light to reach at the surface of earth from sun = 8min

▪ Speed of light = 3×10$^8$mps

To Find :

▪ Distance b/w earth and sun. (in km)

Concept :

☞ Speed is defined as the ratio of distance travelled to the time taken.

☞ It is a scalar quantity.

☞ SI unit : m/s

Conversion :

✏ 1min = 60s

✏ 8min = 8×60 = 480s

✏ 1000m = 1km

Calculation :

$\dashrightarrow\sf\:speed=\dfrac{distance}{time}\\ \\ \dashrightarrow\sf\:3\times 10^8=\dfrac{distance}{480}\\ \\ \dashrightarrow\sf\:distance=1440\times 10^8\:m\\ \\ \dashrightarrow\underline{\boxed{\bf{\purple{distance=1.4\times 10^8\:km}}}}$

Extra Dose :

✈ Distance b/w earth and sun is called as Astronomical unit (AU)

$\gray{\bigstar}\:\boxed{\rm{\red{1AU=1.5\times 10^{11}\:m}}}$