The source of electromagnetic wave can be a charge.
- Moving with a constant velocity
- Moving in a circular orbit
- At rest
- Moving parallel to the magnetic field
The Correct Option is B
Solution and Explanation
The question asks us to identify the source of an electromagnetic wave from the behavior of a charge. To answer this, we need to understand when charges produce electromagnetic waves.
An electromagnetic wave is generated when a charge is accelerated. This is because acceleration of a charge alters the electric and magnetic field around it, leading to the propagation of these field changes as waves through space. Let’s evaluate each option based on this principle:
- Moving with a constant velocity: A charge moving with constant velocity does not experience acceleration. Hence, it does not produce electromagnetic radiation.
- Moving in a circular orbit: When a charge moves in a circular path, it constantly changes direction. This change in direction implies continuous acceleration (centripetal acceleration) even if the speed is constant. This provides a source of electromagnetic waves.
- At rest: A charge at rest has no change in velocity (no acceleration), thus it does not emit electromagnetic waves.
- Moving parallel to the magnetic field: A charge moving parallel to a magnetic field without any change in speed or direction also means no acceleration, and hence, no electromagnetic radiation is produced.
Based on the above analysis, the correct answer is:
Moving in a circular orbit
This is because the charge exhibits centripetal acceleration in a circular path, which is necessary for the emission of electromagnetic waves.
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Concepts Used:
Electromagnetic waves
The waves that are produced when an electric field comes into contact with a magnetic field are known as Electromagnetic Waves or EM waves. The constitution of an oscillating magnetic field and electric fields gives rise to electromagnetic waves.
Types of Electromagnetic Waves:
Electromagnetic waves can be grouped according to the direction of disturbance in them and according to the range of their frequency. Recall that a wave transfers energy from one point to another point in space. That means there are two things going on: the disturbance that defines a wave, and the propagation of wave. In this context the waves are grouped into the following two categories:
- Longitudinal waves: A wave is called a longitudinal wave when the disturbances in the wave are parallel to the direction of propagation of the wave. For example, sound waves are longitudinal waves because the change of pressure occurs parallel to the direction of wave propagation.
- Transverse waves: A wave is called a transverse wave when the disturbances in the wave are perpendicular (at right angles) to the direction of propagation of the wave.