Question

Light travels at a constant speed of about 300,000 km/s. This speed is referred to as the speed of light. A light year is the distance that light travels in one year. One light year is equal to 9.46 trillion kilometers. The closest star to Earth, other than the Sun, is Proxima Centauri. It takes light from this star about 4.2 years to reach Earth. How far from Earth is the star Proxima Centauri? A. 4.2 light years B. 9.46 trillion km C. 300,000 light years D. 300,000 km.

Answer 1

Based on the information in the question, a light year is the distance traveled light in one year. Then if the light from the star Centauri takes 4.2 years to reach the earth, then its distance from earth is 4.2 light years.

Answer 2

The correct choice is

A. 4.2 light years

Step-by-step explanation:

v = speed of light = 300,000 km/s

t = time taken for the light to travel from Proxima centauri to earth = 4.2 years

d = distance traveled by light in 1 year = 1 light year

So

distance in 1 year = 1 light year

distance in 4.2 year = 4.2 light year

Hence

distance of star Proxima Centauri from earth = 4.2 light year