Question

It is known that light from a distant star takes 10 years to reach the Earth. How far is this star situated from the Earth?

a) 9.467 $\times$ ${10}^{16}$ km

b) 9.467 $\times$ ${10}^{16}$​ m

c) 10 light years

• A. only a
• B. only b
• C. both (a) and (c)
• D. both (b) and (c)

Answer 1

The correct option is D

both (b) and (c)

Time taken for light from the star to reach the Earth = 10 years

Distance of the star from Earth = Speed of light $\times$Time taken

= Speed of light $\times$10 years

= 10 $\times$1 light year

= 10 $\times$ 9.467 $\times$ ${10}^{15}$ m

= 9.467 $\times$ ${10}^{16}$ m