Question

What is the speed of all electromagnetic radiation?

Answer 1

Hint: In order to know the speed of any electromagnetic radiation, we shall first see how these waves are generated and then, get a general idea as to what can be the range of speeds of electromagnetic radiation in different mediums. We will also see how this speed was first experimentally calculated.

Complete step-by-step solution:
Electromagnetic waves fall under the category of non-mechanical waves. These are the types of waves that do not require any material medium to transfer energy from one point in space to another, that is, these waves can traverse through vacuum of space too. Generally, when we talk about the speed of electromagnetic radiation, we talk about waves such as, light rays, X-rays, gamma rays, radio waves, microwaves, etc. Also, we talk about their speed in the air.
The speed of an electromagnetic radiation is in range of speed of light, that is, it travels at a speed of $3\times {{10}^{8}}m{{s}^{-1}}$ in vacuum and almost the same speed in air. The speed of an electromagnetic radiation in a medium different then air is given by:
$\Rightarrow v=\dfrac{c}{\mu }$
Where,
‘v’ is the speed of radiation in that medium.
‘c’ is the speed of light in vacuum. And,
‘$\mu $’ is the refractive index of the medium.
Additional Information: The speed of light was first calculated by Danish astronomer Ole Roemer who calculated the speed of light by timing eclipses of Jupiter’s moon Lo. His works were later used by Huygens to give a rough idea of the speed of light. Huygens calculated the speed of light to be 131,000 miles per second whereas the actual speed of light is 186,000 miles per second.

Note: The speed of radiation of any wave exactly is 299,792,458 meters per second which is generally approximated as $3\times {{10}^{8}}m{{s}^{-1}}$ . This is a very important approximation in Physics as the use of original value will greatly complicate calculations at basic or intermediate level.