Question

Which one of the waves cannot be seen through the electromagnetic spectrum?
A. Radio waves
B. Microwaves
C. Infrared waves
D. Ultraviolet waves

Answer 1

Electromagnetic spectrum is defined as the range of all types of electromagnetic radiation. It is known as the range of frequencies, wavelengths and photon energies. The electromagnetic spectrum is further classified as infra – red radiation, visible light or ultraviolet radiation.

Complete answer:
The whole electromagnetic spectrum is given by radio waves, microwaves, infra-red radiation, visible light, ultra - violet radiation, X – rays, gamma rays and cosmic rays in the order of their frequency and in the order of their respective wavelength.
The use of the following electromagnetic waves in our daily life are:
Visible light: These rays are detected by our eyes. Light bulbs, stars, etc, emit visible light.
Radio wave: Radio waves are captured by radios which are transmitted by the radio stations. It is mainly used for TV and mobile communications.
Infra – red: These are widely used in night vision goggles. Devices are used to read and capture the infrared light emitted by our skin and objects with heat.
X – ray: It is used mainly for medical purposes. It is also used in security checks.
Microwave: This radiation is found in microwaves and is useful for cooking. It is also used by the astronomers for determining the structure of stars.
Ultra – violet ray: The sun is the principle source of this radiation.
Gamma rays: It is widely used in medical fields.
The part of the electromagnetic spectrum which is not visible to the human eye are ultraviolet rays, X – ray, and gamma ray. Thus, from the given options ultraviolet waves cannot be seen through the electromagnetic spectrum.

Hence, option (D) is the correct answer.

Note:
In vacuum the electromagnetic waves travel at the speed of light. The electromagnetic waves in different bands have different characteristics depending upon how they are produced, how they interact with matter and their practical applications.