Question

Light travels at approximately $3.0\times {{10}^{8}}{m}/{\sec }\;$, How far does light travel in one week?

Answer 1

Hint: The speed of light is denoted as c is a universal constant in vacuum, we need to calculate the distance traveled by a light in 1 week, so we need to convert one week or 7 days into total number of seconds and we can calculate it.

Formula used:
$D=V\times T$

Complete Step by step solution:
Number of seconds in 1 minute = 60 sec,
Number of minute in 1 hour = 60min,
Number of hours in a day = 24 hours,
Number of days in a week = 7 days

So by multiplying the above four values we can calculate total number of seconds in a week,

Now, total seconds = $60\times 60\times 24\times 7=60,4800\sec $

We know that distance=$speed\times time$ so,
Distance = $3.0\times {{10}^{8}}{m}/{\sec }\;\times 60,4800\sec =1,8144\times {{10}^{10}}m$

Additional information:
Light travels in a uniform substance or medium and propagates in a straight line at constant speed unless for exceptions as reflection, refraction or in with some other sources.

When a light enters in a different medium such as glass or water the speed and wavelength can change but the frequency remains constant irrespective of the medium, light travels at the speed of 300,000 km/s in a vacuum where refractive index equals to 1.

Note:
In the above question we have solved by assuming that light is traveling in vacuum and the speed of light is constant in that otherwise if some medium has been given in some case then we have to considered its refractive index as well and had to solve according to changed speed of light in that medium.