Electromagnetic Waves MCQs

Ans. A. Velocity

Explanation: The frequency, Wavelength, and time period of a wave can all change depending on the source of the wave. The velocity of an electromagnetic wave, on the other hand, is determined by the medium through which it travels.

The velocity of electromagnetic waves in a material medium is given by

\(v=\frac{1}{\sqrt{\mu \epsilon}}\)

Where μ is the permeability of the medium and ε is the permittivity of the medium

The speed of light is the velocity of a wave in a vacuum, which is considered to be 3 × 10⁸ m/s.

Ans. C. Sinusoidal waves

Explanation: A sinusoidal graph depicts electromagnetic waves. It is made up of time-varying electric and magnetic fields that are perpendicular to each other and the propagation direction of waves. The periodic oscillation is described by a sinusoidal wave. The electromagnetic wave is known as a sinusoidal wave because it is represented as a sine curve.

Ans. B. infra-red waves

Explanation: Fluorometers typically have a range of 100 kilometres, meaning they can measure distances up to 100 kilometres. It requires a high-range propagating wave that can reflect the instrument to perform effectively.

Ans. C. Phase difference

Explanation: In general, the numerous EDM systems on the field do not directly monitor transit time. The distance is calculated by calculating the phase difference between the sent and reflected signals, which is only achievable if the process is error-free.

Ans. C. Modulated infrared 

Explanation: Modern EDM employs modulated infrared rays capable of receiving reflected waves from up to 100 kilometres away.

Ans. C. Cycles

Explanation: The phase difference between transmitted and reflected signals can be used to measure the distance between two points in a total station. The phase difference may be stated as a fraction of cycles, which is the most convenient way to calculate and interpret the phase difference.

Ans. B. Gamma rays 

Explanation: Radio waves, microwaves, Infrared radiation, Visible light, ultraviolet radiation, X-rays, and gamma rays make up the electromagnetic spectrum in order of increasing frequency.

Gamma rays have a frequency of > 3 × 10¹⁹Hz.

As a result, in the electromagnetic spectrum, Gamma rays have the highest frequency.

Electromagnetic Spectrum

Ans. A. Polarisation 

Explanation: Polarisation shows that electromagnetic waves are transverse in nature. The wave aspect of light or EM waves is explained through interference and diffraction. Polarisation is a very good phenomenon in which we can use the vibration of waves and it is restricted to a certain direction perpendicular to the propagation direction of W. As a result, the transverse character of EM waves is explained.

Ans. B. Transverse 

Explanation: When the wave's disturbances are perpendicular (at right angles) to the wave's propagation p, it's termed as Electromagnetic waves travel in a transverse direction. They are travelling at a constant phase velocity of v = \(\frac{\omega}{k}\). As a result, they aren't stationary.

Ans. C. γ-radiation

Explanation: The quantity of energy absorbed during radiation penetration is determined by the type of radiation or particle used as well as the type of absorbing material used. High-energy electromagnetic radiation, or high-energy protons, are gamma rays and X-rays. Gamma rays may travel through metals up to a centimetre thick and still be detected on the other side.

Ans. D. Microwaves

Explanation: From longest to shortest wavelength, the electromagnetic spectrum comprises all radio waves e.g., commercial radio and television, microwaves, radar, Infrared radiation, visible light, Ultraviolet radiation, X-rays, and gamma rays in sequence. Since radio waves are not given in the option it makes microwaves the second electromagnetic wave to have the longest wavelength.

Wavelengths

Ans. C. Accelerated charge

Explanation: When electric charges are accelerated, electromagnetic waves are created. This enables the generation of electromagnetic waves by passing an alternating current via a wire, which serves as an antenna. The frequency of the waves produced in this manner is equal to the frequency of the alternating current.

Ans: D. Electromagnetic waves move at the same speed in all mediums.

Explanation: In a vacuum, all EM waves travel at c. In every other medium, however, the speed of an EM wave is determined by frequency. This is why various hues of light refract by varying amounts when white light is sent through a prism, resulting in a rainbow pattern. In general, the speed of a wave depends on the general kind of wave, the frequency of the wave, and the amplitude of the wave for any particular medium.