Diffraction

Reflection vs diffraction is one of the standard search terms. Reflection deals with the light wave and Diffraction deals with light and sound.

REFLECTION	DIFFRACTION
The bouncing of light is termed as a reflection	The bending of light in the corner is termed Diffraction
Reflection is concerned with the incident light bouncing back into the same medium	Diffraction is concerned with sound and light traveling from one medium to another
In reflection, light can be a particle or a wave	In Diffraction, the light has to be a wave

On the basis of the comparison we shall discuss the three of the few factors that helps to different reflection and diffraction:

• Reflection vs Diffraction in terms of velocity
• Reflection vs Diffraction in terms of medium
• Reflection vs Diffraction in terms of incident light

The one main difference between reflection vs Diffraction is that one deals majorly with light and the other with sound, although having light in it. Say when a light beam or a ray passes through a medium, the properties will be affected.

In reflection, the incident light hitting the target will either bounce back to the same medium or enter another medium depending upon the type of the medium.

But in Diffraction, the light beam will pass through the medium in and out and will also accompany sound with the passage. Here the factors like frequency amplitude will remain the same when sound is considered.

One main difference is, in reflection, the incident light can act as both particle and wave, but in Diffraction, the incident light must be a wave.

Reflection vs Diffraction in terms of velocity

In reflection, the velocity of the incident light particle or wave is constant because the speed remains unchanged. But the direction component is changed due to the different angles at which the light has been incident on.

Diffraction has specific quantities which will remain unchanged, but speed is sometimes altered accordingly, which appears to be but, in reality, does not. The incident light is hitting at a different angle on the target, so the end result is also at a different angle.

Since velocity is regarded as the vector quantity, it holds both the magnitude and the direction components, where speed is considered to be the magnitude component of it.

Hence both in reflection and in Diffraction, the speed remains unchanged, but the direction changes at different angles each. The reason is that the speed is constant throughout the process irrespective of the source of the incident light and the target being considered.

When velocity is concerned, both reflection and Diffraction will face no change with speed but with direction.

Reflection vs Diffraction in terms of medium

Reflection of incident light mainly depends on the property of the target. If the target surface is smooth and glassy, the incident light will instantly bounce back into the same medium.

Diffraction does not depend on the medium directly but is connected with the refraction, where the light bends around the corner of the target object. In this case, it comes out as a sound too.

When light enters from a rarer medium to a denser medium, there will be a slight change in the speed of light along with a significant change in direction. The reason is that the denser medium will have a different refractive index than the rarer medium.

When the rarer medium is regarded to be air and the denser medium is water or oil, the light passing from another will face a change in the direction and a change in the speed too.

For example, when a ray of light is incident on a mirror, it will reflect back the exact image of the light in return. This is because the light is reflected back into the medium but at a different angle to that of the incident angle.

But in Diffraction, the light ray will enter another medium will, refract, and will bend around the corner of the medium. For example, if we yell inside a room, the wall will stop the reflection, but the sound will stay within the walls.

Reflection vs Diffraction in terms of incident light

For reflection, the incident light can be a wave or a particle, but for Diffraction, the incident light must be a wave.

When a particle of light is incident on a target surface, it will reflect back into the same medium depending upon the type of target surface, but in Diffraction, the incident ray must be a wave in order to bend around corners.

Like we said earlier, when a particle or a wave strikes on a target surface which is a mirror, it will reflect back the exact same image if the particle or a wave in turn. But in Diffraction, if a wave passes through a pinhole, it will refract in the medium and will come out as different sets of light waves.

So for the light to bend around corners and to pass through a pinhole or any type of medium, the incident light must be a wave in order to produce more waves.

Frequently Asked Questions

What is refraction?

When an incident light passes from one medium to another, it will change the direction and speed.

If any light wave or a particle moves from a different medium, it will face a change in direction and in speed. Depending upon which the refracted ray will either travel towards the normal or away from the normal. The speed and direction in refraction will vary compared to that of the incident light.

What are refracted rays and diffracted rays?

Refracted ray travels towards or away from the medium, and diffracted ray is the result of the bending of light.

In refraction, the incident light can be a particle or a wave and, depending upon the medium, will move away or towards the normal. But a diffracted ray is the one that is passed through a medium, say a pinhole; coming out of it will be another set of a new wave pattern. A diffracted ray has also sound accompanied with it.

Does a sound wave reflect or refract?

A sound wave can be both reflected and refracted. The reflection and the refraction of sound occur according to the type of medium.

A sound wave in a vast hall is certainly reflected because the medium is large, and there is no other second medium for it to enter. So it is reflected back to back, and that’s how a sound is heard in a place. Also, sound waves require a medium to travel without which it cannot be reflected or refracted. When the medium is not very dense, the sound waves refract, and it will not stop at the boundary of the medium.

Also Read:

• Lens diffraction limits
• Diffraction vs refraction
• Diffraction vs dispersion
• Diffraction in telescopes
• Microscope diffraction limit formula
• Telescope diffraction limit formula

In optics, the study of diffraction and dispersion helps us understand the behavior of light, such as the bending and spreading of light when it passes through a medium.

The light wave has the ability to bend and then spread out itself; this behavior of light can be distinguished as diffraction and dispersion. Both terms sound similar, but there are certain natures that differ them from one another. In this post, we give a brief comparison of diffraction vs dispersion of light and their behavior.

Comparison of Diffraction vs Dispersion

The table given below helps you to understand the differences and also similarities between diffraction vs dispersion.

	Diffraction	Dispersion
Definition	When the light strikes the edge of the hurdle, it bends at the corner, creating the geometrical fringes.	The propagation of light waves from one medium to another medium of different refractive indices splits into different wavelengths.
Dependency on wavelength	Diffraction depends on the wavelength of the incident light, as if the light wave of longer wavelength is incident on the slit, it diffracts more.	The spreading up of light waves depends on their wavelength. The light with a shorter wavelength disperse first, and then, in increasing order, they spread out of the medium.
The velocity of the light	The velocity of the light before and after diffraction of light remains constant, i.e., diffraction does not affect the velocity.	There will be a change in the velocity of the incident light as the light is travelling between the two mediums of different refractive indices.
Monochromaticity	The diffraction can be obtained using both monochromatic and polychromatic light. We get diffraction fringes of seven colors in the polychromatic, i.e., using white light and fringes of dark and bright by using the monochromatic light.	Dispersion can be achieved only by using white light or polychromatic light. We do not see the dispersion of waves in monochromatic light.
Dependency on the angle of deviation	Diffraction is independent of the angle of deviation of the light if the monochromatic light is used for the diffraction process. If we are using white light for the diffraction process, it depends on the angle of deviation.	Dispersion entirely depends on the angle of minimum deviation.
Refractive indices of the mediumSince diffraction depends on the wavelength and frequency of the incident light, which depends on the refractive index of the medium, thus diffraction also depends on the refractive indices of the medium of propagation.	The Refractive index of the propagating medium is the leading cause of the dispersion. The dispersion of the light takes place when the light travels from a denser medium to a rarer medium or vice versa of different refractive indices.
Examples	A diffraction grating is the best example of the diffraction of white light. Holograms and CD which reflects the rainbow colors are due to diffraction	When white light travels through the prism, the white light disperses into seven colors of a different wavelength. The formation of a rainbow is also an example of dispersion.

Some interesting points to remember

• Not only light the sound waves can also undergo diffraction as well as dispersion. The diffraction of sound is already discussed in the previous article. The dispersion of sound waves is called acoustic dispersion, in which sounds of different frequencies are separated when a sound wave is passed through a certain medium.
• In some cases, a diffracted light can be dispersed, i.e., when a narrow slit diffracts white light on a grating, the diffracted light is then dispersed into its prominent colors. For example, on the CD, we see the diffraction pattern that disperses into all the prominent colors of the rainbow.
• The reason for dispersion is refraction. When the white light is refracted by a glass prism, we obtain the dispersion of colors of various wavelengths. For example, when the rainbow is formed, we see the seven colors, which are separated accordingly by their wavelength; the white light is first refracted, then dispersed into the colors of the rainbow.

From the study of diffraction vs dispersion, we know that dispersion is related to both diffraction and refraction, depending on the medium of propagation and the nature of the incident light.

Frequently asked questions                                                         

What is meant by angle of deviation?

When a wave passes from one medium to another, the wave may bend, making a certain angle θ. The bent wave that emerges out of the medium is called refracted or diffracted wave.

The incident wave deviated its direction when it propagated between two mediums or slits. The angle between the incident wave and the deviated wave is called the angle of deviation. The angle of deviation on the wavelength of the emerging wave. The angle of deviation can also be given by taking the difference between the angle of the incident wave and the angle of the emerging wave.

How do diffraction and dispersion are related?

If we are talking about white light, then diffraction and dispersion are related.

When white light is passed through a narrow slit, and it is made to an incident on the grating, then we can observe the diffraction pattern on the grating. The diffraction pattern obtained by the grating is the dispersed colours of different wavelengths of light. Thus diffraction is related to dispersion splitting the white light into individual wavelengths.

Does the frequency of wave change during dispersion?

The dispersion is a property of the wave which depends on the speed as well as wavelength. Since wavelength is inversely related to frequency, the dispersion also depends on the frequency.

The shape of the wave pulse changes as it travels from one medium to another medium of dissimilar refractive indices, this change in the shape leads to the change in the velocity of the wave phase, which depends on the frequency. Thus any medium acts as a dispersive medium; there will be a regular change in the frequency.

The dispersion of light can be seen in a prism, not on a glass slab; why?

Even though the glass slab has the ability to refract the incident light, it does not have the ability to disperse the incident light is due to its geometrical structure.

A glass slab is designed with two parallel interfaces, which refracts the incident light and then emerges out of the slab parallel to the incident light; also, they are so closely spaced that splitting up of light would be difficult. However, in the case of a prism, the refractive interfaces are not parallel, and there is a sufficient gap to separate the colors into the desired wavelength.

Also Read:

• Reflection vs diffraction

The behavior of waves traveling from one medium to another medium is different. The difference in the behavior of waves gives the phenomena of diffraction and refraction.

Diffraction and refraction are the processes of change in the direction of the wave. Both the light and sound waves can undergo diffraction and refraction. In this post, we will learn the differences between diffraction vs refraction in both light and sound and learn various facts involved in diffraction vs refraction.

Diffraction vs refraction of light

The comparative analysis of diffraction vs refraction briefly summarizes the nature of propagation light waves in the various mediums. In this section, let us discuss the comparison of diffraction vs refraction of light.

	Diffraction	Refraction
Definition	Diffraction is the bending of light at the corner of the hurdle when the light ray passes through the slit giving geometrical shadow.	Refraction is the bending of light when it travels from one medium to another of different refractive indices.
Wavelength	The diffraction corresponds to the wavelength; as the wavelength is more, the amount of diffraction will be more.	Refraction is also wavelength-dependent; the amount of refraction increases if the wave with a shorter wavelength is incident on the medium.
Nature of the image or pattern	Diffraction of light produces spots or fringes as the diffraction pattern. The pattern is nothing but the shadow of the obstacle.	Refraction of light produces realistic visual illusions or images, not the fringes or shadows.
The appearance of the image or pattern	The diffracted pattern appears where they are, and they do not look closer than their original position.	The refracted image of the object appears to be closer than its original position.
Splitting up of light wave	When white light is diffracted by passing through an obstacle, it splits the light into its prominent colors giving the diffraction pattern.	The refraction also has the ability to splitting up white light into its prominent colors.
Intensity	The intensity of the diffraction fringes depends on the nature of incident light and the width of the slit.	The refracted light’s intensity depends on the light’s velocity and the refractive indices of the medium.
Examples	At the edge of the door or window, the bending of the light ray produces the shadow of the window or door.	Water in a swimming pool looks less deep is due to the refraction of light.

Diffraction vs refraction sound

The change in the direction of the sound wave can produce diffraction as well as refraction depending on the nature of the medium and material. The differences between acoustic diffraction vs refraction is listed as follows:

	Diffraction	Refraction
Definition	The diffraction of sound waves involves a single medium where the bending of the sound wave takes place, and then the sound wave spreads out.	The refraction of the sound waves involves the bending and spreading of the wave, and hence the speed of the sound wave changes. The speed may increase or decrease depending on the nature of the medium.
TemperatureThe diffraction of sound waves is generally a temperature-independent phenomenon.	The refraction of sound waves generates a natural temperature gradient for the atmosphere.
Wavelength	The wavelength of the sound wave plays a vital role in the diffraction of sound. The greater wavelength sound wave diffracts more than, the shorter wavelength wave.	If the wavelength is shorter, the frequency will be high; this makes the sound wave attain a higher pitch, and thus the refraction will be greater.
Size of the passage	The size of the passage contributes to the diffraction. The diffraction of the sound wave is more if the passage is smaller.	Since the refraction of a sound wave is caused by traveling from one medium to another, the size of the passage or medium does not matter; the only thing that matters how dense the medium is.
The velocity of the wave	The velocity of the sound wave remains the same before and after the diffraction.	Refraction is caused due to change in direction, and thus, the velocity also changes when the refraction of a sound wave happens.
Examples	Forest-dwelling birds hear the sound of other birds in the long-distance is due to the diffraction of the sound wave at the edge of the trees.	The thunder sound created during lightning is a good example of the refraction of the sound wave.

Is refraction same as diffraction?

Diffraction and refraction are very important properties of the wave where bending or spreading of the wave occurs. These are natural phenomena that can be observed everywhere around us. Though both properties encounter bending phenomena, they differ from one another.

Refraction is a bulk phenomenon; it occurs when the wave hits a surface and travels through the bulk of another medium of different densities, and the bending of the wave takes place. While the diffraction is an edge phenomenon, where the wave hits the corner of the obstacle, which is placed in the path of the propagation of the wave, and then bending or spreading of the wave takes place.

Though both diffraction and refraction are the characteristics of the wave, their result is also different as the refraction produces the visual image, whereas the diffraction produces the fringes or geometrical shadows.

Is it a rainbow diffraction or refraction?

Rainbow is a naturally occurring process in the sky when the light ray from the sun passes through the water droplet.

Even though the rainbow looks like the cause of diffraction as the water droplet acts as a grating because water is a transparent medium, diffraction does not play any role in the rainbow formation. As the light ray travels from the water droplet to air, there is a change in the light ray’s propagation medium. The refractive indices of air and water are different. As the water medium is denser than the air medium, there will be refraction, not diffraction.

The cause of the rainbow

• The cause of the rainbow is due to the refraction, and reflection also plays a part in causing the rainbow. When the light ray enters the water droplet, the ray gets reflected inside the droplet more than once; this is called total internal reflection, which causes the rainbow to look shiner. When the ray leaves the droplet, the rays are double refracted, and they disperse into a cone of seven constituent colors of various wavelengths.

Is a prism refraction or diffraction?

The prism has the ability to disperse the white light into its constituent colors when white light is passed through the prism. The dispersion of white light in the prism is due to refraction, not diffraction.

When the white light ray is encountered on the prism, the bending of the light ray takes place at the surface of the prism. Since prism is made up of a particular type of glass-like material, the refractive index of the prism is more than the air; the splitting up of colors takes place inside the prism of a different wavelength.

The spectrum we obtained from the prism of different frequencies is not the diffraction pattern. Prism is refraction, not diffraction.

Each spectral line emerges out of the prism, and the rainbow has a different wavelength in the order of red, yellow, green, blue-green, blue, and violet. Red has the longest wavelength, and violet has the minimum wavelength.

Some interesting facts of diffraction and refraction

• The refraction is the property of the wave that obeys “Snell’s law”.
• Not only light and sound waves, electromagnetic can also undergo refraction and diffraction.
• The amplitude of the wave decreases after the refraction and diffraction, as there is a change in the direction of the wave; hence during the process, some amount of energy may get lost; as a result, there will be an amplitude decrease.
• Water can undergo both refraction and diffraction as it is a transparent medium. For example, if we place a straw in a glass of water, it looks like the straw is cut off; in this case, water acts as a refractive medium. While if a light wave hits the island and bends, it produces the shadow of the island due to diffraction.
• On the earth, we can able to visualize maximum of ¾th of the rainbow cone; a pilot can visualize the complete rainbow.

Also Read:

• Telescope diffraction limit formula
• Diffraction vs dispersion
• Reflection vs diffraction
• Lens diffraction limits
• Microscope diffraction limit formula
• Diffraction in telescopes