NEET Practice Questions (MCQs) with Answers & Solutions

Infrared radiations are detected by bolometers. A bolometer is a device that measures the power of incident electromagnetic radiation via the heating of a material with a temperature-dependent electrical resistance.

In an electromagnetic wave, the electric field ($\vec{E}$) and magnetic field ($\vec{B}$) are always perpendicular to each other and also perpendicular to the direction of propagation of the wave. Thus, the statement '$\vec{E}$ is parallel to $\vec{B}$' is incorrect.

Among the given options, radiowaves have the least frequency. The electromagnetic spectrum is ordered by increasing frequency as follows: radiowaves < microwaves < infrared radiation < x-rays.

Electromagnetic waves have varying wavelengths, from long radio waves to very short gamma rays. Among the given options, ultraviolet rays have the shortest wavelength. Radio waves have the longest wavelength, followed by microwaves, visible waves, and then ultraviolet rays. Hence, ultraviolet rays have the least wavelength.

Transverse waves are waves in which the movement of the medium is perpendicular to the direction of the wave. Electromagnetic waves, such as light, x-rays, and microwaves, are transverse waves. Sound waves in air are longitudinal waves, where the movement of the medium is in the same direction as the wave. Therefore, sound waves traveling in air are not transverse in nature.

Electromagnetic waves are not deflected by electric or magnetic fields because they consist of oscillating electric and magnetic fields that propagate through space. The fields are self-perpetuating and do not require a medium, hence they are not influenced by external electric or magnetic fields. Therefore, the correct option is 'none of these'.

When an electromagnetic wave encounters a dielectric medium, the transmitted wave has the same frequency but different amplitude. The frequency of the wave remains unchanged because it is a property of the source of the wave. However, the amplitude changes due to the interaction of the wave with the medium, which can either absorb or reflect some of the wave's energy.

According to Maxwell, a changing electric field produces a magnetic field. This is one of the key components of Maxwell's equations, which describe how electric and magnetic fields propagate and interact. Specifically, a time-varying electric field induces a magnetic field, and vice versa.

James Clerk Maxwell was the first to predict the existence of electromagnetic waves. In 1864, Maxwell's equations showed that electric and magnetic fields could propagate through space as waves moving at the speed of light. This theoretical prediction was later experimentally confirmed by Heinrich Hertz.