Question

Light from the sun reaches the earth approximately in
A. 5s
B. 50s
C. 500s
D. 0.5s

Answer 1

Hint: The outer space is considered to be vacuum there is no medium for any wave to travel:
Light does not need any medium to travel. Light can travel in Vacuum.
Light is the wave of photons emitted by the sun.

Complete step by step answer:
We know that the speed of light in a vacuum is approximately 300,000 kilometres per second
Mathematically the speed of light can be written as
\[C = 3 \times {10^8}m{s^{ - 1}}\]
Now the distance of the sun from the earth is nearly 149,600,000 kilometres
Mathematically it can be written as
$d = 1496 \times {10^8}m$

Now for simple distance-time calculation
We have got speed and we have got distance now we just have to calculate the time
So in general terms, a photon has been emitted from the sun at a speed of \[C = 3 \times {10^8}m{s^{ - 1}}\] and it needs to travel a distance $d = 1496 \times {10^8}m$ to reach the earth
Now we need to calculate the time
As we know that $S = \dfrac{d}{t}$
$\therefore t = \dfrac{d}{S}$

Here the speed of light is denoted by C instead of S
So,$t = \dfrac{d}{C}$
Substituting the values we get
\[t = \dfrac{{1496 \times {{10}^8}m}}{{3 \times {{10}^8}m{s^{ - 1}}}}\]
$ \Rightarrow 498.66\sec \approx 500\sec $

Here as we can see our value is coming out to be 498.66 seconds but we can round it off to 500 seconds because there is a little amount of uncertainty in the values of speed of light and distance of the earth from sun because there are non terminating rational numbers.

Hence, the correct answer is option (C).

Note: Light doesn’t need any medium to travel. This is evident from the fact that there is no material medium present in outer space so technically making it a vacuum but the light emitted by the sun still reaches to earth.