Question

How many meters are there in a light year?

Answer 1

Hint: Light is one of the fastest elements in the universe. The speed travelled by it in vacuum is the speed of light. In one year, the distance that light travels is a light year. In order to convert light years into metres, we use the speed of light to calculate the distance by it in seconds, hours, days etc.

Complete answer:
Light is defined as the distance travelled by light in one year. We know that the speed of light is $3\times {{10}^{8}}m{{s}^{-1}}$. This means that the distance travelled by light in one second is $3\times {{10}^{8}}m$. Therefore, the distance travelled by light in one hour will be-
$3\times {{10}^{8}}\times 60\times 60=108\times {{10}^{10}}m$
The distance travelled by light in one hour is $108\times {{10}^{10}}m$. One day is made of 24 hours, so the distance travelled in one day will be-
$108\times {{10}^{10}}m\times 24=2592\times {{10}^{10}}$
The distance travelled by the light in one day is $2592\times {{10}^{10}}$.
One year is made of 365 days, therefore, the distance travelled in one year in metres will be-
$2592\times {{10}^{10}}\times 365=9.5\times {{10}^{15}}m$
The distance travelled by light in one year is $9.5\times {{10}^{15}}m$.
The distance travelled by light in one year is equal to one light year which is equal to $9.5\times {{10}^{15}}m$.
Therefore, there are $9.5\times {{10}^{15}}m$ in one light year.

Note:
Light is an electromagnetic wave, it is made of electric and magnetic fields oscillating perpendicular to each other as it is the visible part on the spectrum of electromagnetic radiation. It does not require a medium to travel. Light years are also used as a unit to represent very large astronomical distances.