Reflection of Electromagnetic Waves from a Wall

Introduction:
When electromagnetic waves encounter a boundary or a wall, they can undergo reflection, transmission, or absorption depending on the properties of the boundary and the incident wave. In the case of reflection, the incident wave bounces off the surface and travels in a different direction.

Wavelength along the Wall:
When electromagnetic waves are reflected at an angle from a wall, their wavelength along the wall is greater than in the actual direction of propagation. This means that the wavelength parallel to the wall is longer compared to the wavelength perpendicular to the wall.

Explanation:
When an electromagnetic wave approaches a boundary at an angle, it interacts with the boundary and gets reflected. The angle at which the incident wave strikes the boundary is called the angle of incidence (θi), and the angle at which the reflected wave leaves the boundary is called the angle of reflection (θr). According to the law of reflection, the angle of incidence is equal to the angle of reflection.

Effect of Reflection on Wavelength:
When a wave is reflected, its wavelength does not change. The wavelength is determined by the source of the wave and the medium through which it propagates. However, the direction of propagation changes after reflection.

Doppler Effect:
The Doppler effect is a phenomenon that occurs when there is relative motion between the source of a wave and the observer. It causes a change in the observed frequency and wavelength of the wave. However, in the case of reflection from a wall, there is no relative motion between the source and the observer. Therefore, the Doppler effect does not influence the wavelength of the reflected wave.

Greater Wavelength along the Wall:
When an electromagnetic wave is reflected at an angle from a wall, the angle of incidence is different from the angle of reflection. This change in direction causes the wavelength of the wave to be longer along the wall compared to the wavelength in the actual direction of propagation. This phenomenon is known as wavelength elongation or wavelength stretching.

Conclusion:
In summary, when electromagnetic waves are reflected at an angle from a wall, their wavelength along the wall is greater than in the actual direction of propagation. This occurs due to the change in direction during reflection and is not influenced by the Doppler effect.