Question

Mention one use of part of electromagnetic spectrum to which a wavelength of $21cm$ emitted by hydrogen in interstellar space belong

Answer 1

Electromagnetic Spectrum:

1. The electromagnetic spectrum defines the range of frequencies and wavelengths of the electromagnetic spectrum.
2. The waves with minimum wavelength and maximum frequency are gamma rays and the waves with maximum wavelength and minimum frequency are radio waves.
3. The wavelength of radio waves lies between $1mm$ to $10,000km$. Thus, the wavelength of $21cm$ lies in Radio waves.
4. Here is a diagram which represents the wavelengths of different waves:

Use of radio waves in communication devices,

1. Mostly, radio waves are used in communication devices, such as televisions, mobile phones, and radios.
2. They receive the radio waves and convert these waves into mechanical vibrations in order to produce sound in these devices. Thus, one-way or two-way communication is possible in these devices.

Hence, a wavelength of $21cm$ emitted by hydrogen in interstellar belongs to Radio waves is used in communication devices.