Answer:
635 years old
Explanation:
The light reaching the earth from the sun will travel at a speed called the speed of light, and this has a universal value of 3 × 10⁸ m/s. Bearing this in mind, let us calculate the age of the light reaching the Earth from the sun:
Distance of star from Earth = 6.1 × 10⁸m
Speed of light = 3 × 10⁸ m/s
We have distance and speed, let us calculate the time of travel of the light from the star to the earth.
Distance = speed × time
6.1 × 10⁸ = 3 × 10⁸ × time
In order to do the division above, we will divide the whole numbers normally, then we will apply the law of indices to the power that says:
Xᵃ ÷ Xᵇ = X⁽ᵃ⁻ᵇ⁾
Next, we are told that there are 3.2 × 10⁷ seconds in a year.
∴ The number of years travelled by the light from the star:
please note that:
2.03 × 10¹⁰ = 20300000000
3.2 × 10⁷ = 32000000
The closest answer in the option is 635 years, and we are short of this by some points due probably to approximations in the calculation.