Question

How long does it take to get to the sun from the earth?

Answer 1

To measure time that how much it takes from the earth we need two quantities, one is distance between earth and the sun, and the second one speed that we are travelling from the sun to the earth.

Formula used:
$s=\dfrac{d}{t}$
Here,
$t$ = time.
$s$ = speed which we will take as speed of light ‘C’
$d$ = distance between sun and the earth.

Complete step by step solution:
In this solution we have to find time using distance between sun and earth and the speed of reference that we are taking.
If we take light as a reference for travelling so that we can take speed of light which is
$C=3\times {{10}^{5}}km/s$
Now we know that distance between sun and the earth is
$d=147.2\times {{10}^{6}}km$
Now formula for the speed is
$\Rightarrow s=\dfrac{d}{t}$
So we can say time taken from earth to sun is,
$\Rightarrow t=\dfrac{d}{s}$
Now,
$t=\dfrac{d}{c}....\left( 1 \right)$
Now substitute all the values in the equation (1)
$\begin{aligned} & t=\dfrac{147.2\times {{10}^{6}}}{3\times {{10}^{5}}} \\\ & \Rightarrow t=49.0675\times {{10}^{1}} \\\ & \Rightarrow t=49.0675 \\\ & \Rightarrow t=818\text{ minute} \\\ \end{aligned}$

Therefore, we can conclude that it will take 8.18 light minutes from the earth to sun.

Additional information:
Properties of light:
>Reflection of light: The law of reflection that states that the angle of incidence is equal to the angle of reflection is followed by any light.
>Refraction of light: Refraction of light occurs as it travels from one medium to another medium when the light ray changes its velocity. The refraction index is used as a way of calculating how much light reflected.
>Dispersion: Dispersion of light is defined as the process in which white light, based on its wavelength separates into different colors as it passes.

Note:
As an approach to solve this question first we write a formula for the time and take light as a reference for travelling from earth to sun to derive time from the earth to sun. Additionally, it is very important to make sure before substituting the values in the formula that the units are in the same system i.e. SI unit system.