Refraction of Light : Definition, Causes & Problems With Solution

Light is an essential energy form that can go through various phenomena such as reflection, refraction, diffraction, polarisation, and interference. In that, we will be discussing refraction in detail in this article.

Refraction is a term that occurs while bending the light, which is traveling from one medium to another. This article will also talk about other refraction-related phenomena.

What is the Refraction of Light?

Refraction of light is nothing but the bending of a light wave that goes through different mediums at once. This bending occurs due to the dissimilarities between the substances. In most cases, density varies vastly. In simple words, refraction definition includes the change in the wave direction, which is passing from one medium to the other.

The refraction of light is a very commonly used phenomenon. Various waves like water waves and sound waves are capable of experiencing refraction. It is also one of the main reasons we have optical instruments. Some of these instruments and devices include prisms, lenses, and magnifying glasses. Another main usage of refraction can be seen in our retina functions. Light refraction helps us focus light on the retina.

Causes of Refraction

Whenever the speed varies, there will also be a change in direction. Refraction of light rays occurs when it travels into the medium at an angle containing multiple refractive indexes. Due to the varied speed, a change in direction will take place. For instance, imagine air traveling into the water. Now, the light’s speed will decrease because it is subjected to travel at a varied angle.

Take a look at the refraction of light diagram below to understand the concept better.

The above-shown figure describes the refraction of light. When the light begins to travel from air into glass, there will be a slight change in direction. Also, the refracted light is capable of bending towards the normal line when the lights start to travel from a less dense medium to a denser medium.

In addition, the light wave goes through the boundary in a perpendicular direction. Therefore, we can understand that the light ray does not refract even though there is a change in speed.

Laws of Refraction of Light

The following are some of the main laws of refraction of light:

• Snell’s law of refraction describes the ratio of the angle of incidence’s sine to the angle of refraction’s sine, which gives a constant. The following is the representation of the same:

sin i / sin r = constant

• The refracted ray, incident ray and normal interference of both media are capable of lying on the same plane. It appears to be present at the point of incidence.

Refractive Index

The other name for the refractive index is the index of refraction. It defines the speed of light that can travel through the material.

The index of refraction does not have any dimension. The refractive index can be obtained for a provided material by using the ratio of the light’s speed in vacuum (c) to the light’s speed in medium (v).

The index of refraction can be denoted by n, and the following is the formula for it:

n = c/v

According to the medium’s refractive index, the light ray can change its direction or bend at the junction separating both media. A light ray bends away from the normal or towards the normal when it travels from one medium to the other, consisting of a larger refractive index.

Light Refraction in Real Life

Let us have some understanding of how refraction of light takes place in real life:

• While passing white light through a prism, it is capable of splitting into its component colors. These colors include orange, red, violet, blue, green, and yellow. It is because of the refraction of light.
• The rainbow formation is an ideal example of light refraction. The process of the formation of a rainbow involves the bending of the sun’s rays through the water droplets.
• The actual appearance of a swimming pool always looks less deep than usual. It is mainly because due to the refraction of light, it comes from the bottom and bends at the surface. 
• Other light refraction examples include looming and mirages. These are optical illusions.

Light Refraction Applications

Refraction consists of various applications in optics and technology. Listed below are some of the most prominent ones:

• The usages of refraction can be seen in house doors, peepholes, telescopes, movie projectors, and cameras.
• Light refraction plays a crucial role in helping people with defective vision by allowing them to see through refractive spectacles. Here, the principle of refraction has been used.
• Magnification is another phenomenon where refraction of the lens is used. Here, these lenses utilize refraction in order to form an object’s image for several purposes.

Refraction Problems

Q1. A light traveling in air enters into an optical fiber with 1.44 as its refractive index. Address the following concerns:

1. What will be the bending direction of the light?
2. What will be the refraction angle when one of the fiber’s incidence angles is 22°?

Solution:

1. a) The light will travel from air (rarer medium) to an optical fiber (denser medium). Therefore, it is possible that the refracted ray might bend towards the normal.
2. b) The following is the procedure for calculating the angle of refraction:

Consider air as the 1st medium while optical fiber as the 2nd.

Thus,

n₁= 1.00, n₂= 1.44 and Ө₁₌ 22°.

Substitute the values in the equation as done below:

(1)22°  = 1.44 sin₂.

sin₂  = (1 / 1.44) sin  22°  = 0.26 

Ө₂ =  (0.26)  = 15° 

Q2. Light is travelling through an optical fiber. It reaches the optical fiber’s end and enters the air. The angle of incidence at the tube’s end is 30°. Now, what will be the refraction angle outside the fiber?

Solution:

Consider fiber as the 1st medium and air as the 2nd.

Hence, n1 = 1.44, n2 = 1 and Ө1 = 30°

Now, substitute the values in the equation. We will obtain:

(1.44) sin  30°  = 1 Ө₂  

Ө₂   = (1.44/1 ) sin  30°  = 1.44 (0.5) = 0.72 

Ө₂   =  (0.72)  = 46° 

Here, we can notice the refraction angle seems larger than the incidence angle. It represents the bending of light happening away from the normal when it enters the rarer material.

Conclusion

In conclusion, we have gone through every nook and corner of the refraction concept, starting from refraction definition, refraction of light, and refraction of light diagram, where we understood the basic concepts. In addition, we have also seen the causes of refraction and the laws of refraction. Here, we were able to grasp intermediate knowledge of the topic.

Furthermore, we have gone through real-time examples and applications that portray light refraction in detail. Finally, we have also seen some solved problems with the refraction of light.

Frequently Asked Questions

Q1. How does refraction take place in stars?

A. Twinkling of stars in the earth’s atmosphere is a very interesting example of the refraction of light. It can be termed atmospheric refraction. The starlight, before it reaches the earth, goes through various refractions. This kind of atmospheric refraction is capable of taking place in a medium where there presents a slowly modifying refractive index.

Q2. Define light.

A. Light is an energy that helps us see things. It is very bright. Light begins from an energy source and then bounces off objects by the eyes. The brain uses certain techniques to process this signal, followed by enabling us to see.

Q3. Does light always refract?

A. Light is capable of refracting while traveling at a certain angle into a medium. This medium contains a varied refractive index, i.e., optical density. Change in the speed of light is the main reason for this direction change. For instance, light is slowed down when it travels from air into water. Even though it was subjected to distraction, it travels at a different angle and direction.

Q4. Is it possible to refract sound?

A. Usually, when a wave is refracting, it involves a modification in direction while passing through multiple mediums. Refraction, also termed bending of waves, can be accompanied by a modification in the wavelength and speed of the waves. Therefore, waves’ speed is also subjected to a change whenever there is a change in the medium. Furthermore, sound waves can travel over water.

Q5. What are the materials that refract light?

A. There are three materials that can refract light. They are air, water and glass. Whenever the light rays enter any of these materials, they will be subjected to a change. The refraction angle and the amount of light bending are completely dependent on the refractive index of both media.

Q6. What are the waves that can be refracted?

A. Refraction takes place with all wave types. For instance, waves that move across deep water can travel faster than those that move across shallow water. 

Another example is the light ray passing through a prism (made of glass) that can be bent or reflected.

Q7. Can wavelength affect refraction?

A. As the light’s wavelength decreases, there will be an increase in the refraction amount. The lights that have shorter wavelengths, namely blue and violet, are slowed more. They also experience more bending than orange and red, which are of longer wavelengths.