Reflection of Waves

What is the definition of the reflection of waves?

When a wave strikes any interface that is a boundary between two mediums, it tends to bounce back with the change in direction. This phenomenon of waves is called the reflection of waves. 

Reflection is a phenomenon of the medium. There could be numerous factors that affect reflection and other phenomena as such. Reflection causes certain disturbances in the original energy of the wave. Reflection can easily deteriorate the entire point when it comes to energy change. 

There are two types of interfaces:

1. Open boundary – when a particular wave strikes an open boundary interface, it tends to get reflected and refracted. Complete balancing back of the wave is not observed. The open boundary reflection provides easy propagation of the wave; the movement on the boundary is very certain.
2. Closed boundary – it is said to be a secure boundary when there is a rigid boundary that helps to reflect back the entire wave. One of the best examples of closed boundaries is waves striking the wall. The propagation of the wave in a secure boundary is not as swift as when seen in an open limit.

Reflection on the closed boundary or Fixed end reflection

Reflection on a closed boundary is when you pass a wave on a string that is tied on the wall from one end and free from the other. When a certain incident force hits the wall, it creates pressure on the wall. 

By following Newton’s third law of motion, the wall or other hand also returns this pressure force in an equal and opposite way. This causes the reflection of the given wave. 

You must know that the wall is a rigid boundary, and it won’t move; hence there is no generation of the wave at the edge. Therefore, to make it clear, the wave’s amplitude at the junction becomes zero. 

One might also keep in mind that in such a case, φ=π. The reflected wave and the incident wave at the boundary collapsed with each other and became zero. This is the reason why we say so. 

The point to be remembered here is that when wave reflection takes place, which involves a close boundary, there will always be a reversal of the direction of the wave, and the face of the wave could be said to be reversed. Hence the value becomes 180.

Reflection at an open boundary or Free end reflection

Reflection at an open boundary could be imagined as a wave on the string that is completely free of any attachment. This implies that the wave will travel without any hindrance. In such cases, special pulses at the boundaries are generated. Hence the amplitude of this reflection gets increased. Such an amplitude gets at the max level in the open border.

Both the reflected wave and also the incident wave are in the same phase in an open boundary reflection. Hence the value of the difference between the phases becomes φ=0. 

Law of Reflection

When we talk of the law of reflection regarding the waves when incident light hits a certain medium, there are two possibilities: refraction or reflection. The wave that moves towards the medium is the incident wave. When the incident wave strikes the medium, it can rapidly be absorbed by the medium. When it passes through the medium, the wave changes direction, and there are certain laws on how the wave changes the focus. 

Specular reflection

Any reflection from a mirror or similar surface, where all the light waves striking the surface gets reflected back is known as specular reflection. This is the most common type of reflection. 

Diffuse reflection

The diffuse reflection is the more practical reflection witnessed. In most cases, the light wave hits the surface medium or mirror at an imperfect angel. The light wave hits the imperfections on the reflecting surface, and gets reflected in certain inferior angles. 

Reflection of light waves and the laws of reflection

When discussing the laws of reflection, there are three major laws related to it. These are:

1. When a light wave strikes a mirror or a reflecting surface, the incident ray forms a certain angle with the normal. The angle between the incident ray and the normal is exactly the same as the angle formed between the normal and the reflected beam. On any surface, the rise would be the same.
2. When light strikes a surface, the incident ray, the reflected ray, and the normal all lie in the same plane. 
3. The incident ray and the refracted ray are basically on different sides of the normal. 

Cause of Reflection

Reflection is a phenomenon that only happens when the reflecting media is appropriate. There could be various reasons why light is scattered. 

1. When the plane reflecting surface is smooth and shiny, reflection can easily occur. On the other hand, depending on the quality of the medium, the energy of light is absorbed or reflected back. 
2. When the reflecting surface is not smooth, or is rough, there could be a scattering of light. The laws of reflection are still maintained at every angle. 

Characteristics of the wave motion

The main characteristics of the wave motion are: 

1. Direction – The direction of the wave after and before reflection is something to be taken care of. The main angle formed between the reflected ray and the incident ray would be 90 degrees, and an angulation change is witnessed during the process.
2. The angle of reflection – The rise of reflection becomes very important. When we talk of the main characteristics of a wave, the angle of reflection is the main angle formed between the normal and reflected waves. If this angle is compromised, there is no chance of getting the entire reflected wave back.
3. Wavelength – A wavelength is measured from one peak to the next, or from one trough to the next (which may be a sound wave, an electromagnetic wave, or any other wave). The crest of the wave is the highest point, while the trough is the lowermost point. Considering wavelength is a unit of length, it is measured in meters, centimeters, millimeters, nanometres, and other units of length.
4. Frequency – When we talk about the frequency of the wave, it is the different numbers that pass a fixed place under a certain amount. The frequency of the reflected wave is exactly the same as that of the incident wave, and this is a big characteristic to be noted. It determines the number of waves. 
5. Speed – The speed of the wave is the main velocity of the wave. It is the speed with which the wave travels. 

Conclusion

Above this article, we have mentioned some of the most important points you should know about the reflection of waves. There could be numerous changes in a reflection process depending upon the surrounding where waves travel. A light could be a wave, or it could be a particle. It has dual nature; hence the propagation is highly dependent on the matter.