What Is Refraction? Definition, Laws, and Practical Applications
The changing of the path of a light wave while passing from one medium to another medium is called refraction. Refraction is a common phenomenon that occurs in light waves, sound waves and in water waves.
The amount of refraction is determined by the change in the speed of the light wave and the direction of the refracted wave with respect to the initial direction of the wave.
Refraction of light is a common phenomenon that occurs in our day to day life. An object submerged in water appears closer than it really is when viewed from above. This concept is behind the working of optical lenses. It is used in instruments like glasses, binoculars, cameras, microscopes, and the human eye. Some natural phenomena, like rainbows and mirages, are also due to refraction.
Laws of Refraction
Refraction is based on Snell's law. It states that for a given pair of media the ratio of the sine of the angle of incidence (θ1) to that of the sine of the angle of refraction (θ2) is equal to the ratio and is of the first media with respect to the second media. Further, it is equal to the refractive index of the first medium with respect to the second medium (n2 /n1).
The Refractive index determines the amount of bending of light. It also establishes relations among angle of incidence, angle of refraction, and the refractive index. Mathematically, for a given pair of medium refractive index is given by:
sin θ1/sin θ2 = n2/n1
State the Laws of Refraction of Light
The angle between the incident & the normal ray is called the angle of incidence 'i', and the angle between the refracted ray & normal is called the angle of refraction 'r'. The laws of refraction of light are:
The normal, the incident & the reflected ray; the entire rays lie in the same plane.
The ratio of the sine of angle of incidence & sine of angle of refraction is a constant and is called a refractive index.
The law of refraction, also called Snell's law, determines the behavior of light-rays when it passes from one medium to another medium.
Consider a ray of light incident on a plane interface between two transparent dielectric media, as shown in the figure below. According to the law of refraction, the normal, the incident ray, and the refracted ray all lie in the same plane. Also,
n1 sinθ1 = n2 sinθ2
Where,
θ1 = angle of incidence,
θ2 = angle of refraction.
n1 = refractive index of 1st medium.
n2 = refractive index of 2nd medium.
Thus, according to the law of refraction, light deviates towards the normal in an optical medium with the higher refractive index.
Note that n2>n1 in the figure.
(Image will be Updated soon)
The refractive index of a dielectric medium having dielectric constant K is represented by the formula:
n = √k
The table shows the refractive indices of some materials by using yellow light of wavelength λ = 589 nm.
To Verify the Laws of Refraction of Light
(Image will be Updated soon)
The incident ray, the refracted ray & the normal all lie in one plane for a given pair of media. Also, the ratio of sine of angle of incidence to that of sine of angle of refraction is a constant.
sin i /sin r = μ
Where,
μ = refractive index of the 2nd medium with respect to the 1st medium.
Place a rectangular glass slab on a white sheet of fixed paper on a drawing board.
Trace the boundary of the glass slab as ABCD.
Now remove the glass slab and draw a line of normal N1N2 at O.
Draw a straight line IO inclined at an angle (let say 300) with the normal. IO is the incident ray.
Fix two pins, pin P, and pin Q on the incident ray IO.
Place the glass slab within the boundary ABCD.
Fix two other pins R and S so that, when seen from the other side of slab P, Q, R, and S appear to lie in a straight line.
Remove the glass slab and the pins after marking the pinpoints P, Q, R, and S.
Join point R and S and produce the line on both sides. The ray O'E is the emergent ray.
Join OO', which is the refracted ray.
You can notice that the incident ray, the refracted ray and the normal are in the same plane. This proves the 1st law of refraction.
Let's Prove the Second Law of Refraction
Draw a circle of radius 'R' with O as the center, such that it cuts the incident and refracted rays at F and G, respectively
Draw perpendiculars from F and G to N1N2
FHO and GKO are right-angled triangles.
sin i = FH/OF
sin r = GK/OG
μ = sin i / sin r
μ = FH/OG * OG/GK
μ = FH/GK
Measure the lengths of FH and GK and write them in a table.
Do the same for different angles of incidence.
Find the ratio FH/GK for different values of incidence 'i'.
It is found that FH/GK has a set value for each observation.
This proves the laws of refraction.
How to learn Refraction - Laws of Refraction and Important FAQs?
Learning Refraction - Laws of Refraction and Important FAQs can be a little tough. It is one of the most important concepts of Physics that requires an ample amount of your time and attention. With Vedantu, you can make the learning process a lot easier. We provide you with notes on Refraction - Laws of Refraction and Important FAQs in lucid language that makes the topic easy to learn and understand. By learning Refraction - Laws of Refraction and Important FAQs from our learning platform, you can improve your chances of scoring the highest marks in your exam. Apart from this, here are some other tips to start learning the Refraction - Laws of Refraction and Important FAQs:
While studying the concept of Refraction - Laws of Refraction and Important FAQs, you should highlight or note down the important parts of the topic. You can use these notes for quick revisions during your exam preparations.
When you are learning Refraction - Laws of Refraction and Important FAQs, read the definitions and explanations thoroughly to understand the concept more clearly.
Once you are done with the textbook explanation, you can use other study materials such as revision notes and textbook solutions to improve your understanding of Refraction - Laws of Refraction and Important FAQs.
After learning the Refraction - Laws of Refraction and Important FAQs, you should try solving questions from the exercise in textbooks and reference guides to enhance your knowledge.
You can use solved examples to understand the practical part of Refraction - Laws of Refraction and Important FAQs. These examples will also give you an idea of how to solve practical questions related to refraction.
Before you try to solve the practical problems, you should go through the theoretical part of Refraction - Laws of Refraction and Important FAQs. It will help you gain more knowledge on the concept and solve the questions more easily.
Once you have a clear understanding of the Refraction - Laws of Refraction and Important FAQs, you should use sample papers and previous year physics question papers to understand the type of questions that can come in your final exam.
Try to clear all your doubts related to Refraction - Laws of Refraction and Important FAQs with your teachers before the exam to ensure you do not misunderstand any concept.
Why is it Important to Learn Refraction - Laws of Refraction and Important FAQs?
It is important to learn Refraction - Laws of Refraction and Important FAQs for all the students. By learning about refraction, you can understand the changes in speed and wavelength of length. You can also differentiate between refraction and reflection by learning the concept of Refraction - Laws of Refraction and Important FAQs. Moreover, the solved examples of Refraction - Laws of Refraction and Important FAQs provided by Vedantu will help you solve different kinds of questions based on this concept with ease. Below are some of the other reasons why you should learn Refraction - Laws of Refraction and Important FAQs:
Learning about Refraction - Laws of Refraction and Important FAQs will give you a better understanding of lenses and mirrors that are crucial concepts of physics.
Refraction - Laws of Refraction and Important FAQs is one of the most vital parts of the Physics syllabus. So, by learning the concept of refraction, you can score significantly well in your final exam.
With Refraction - Laws of Refraction and Important FAQs, you can understand how lenses work, how a glass prism splits light into different colours, and why the water in a swimming pool always appears to be shallow.
Once you have completely understood Refraction - Laws of Refraction and Important FAQs, you will be able to solve any type of question that comes in your exam.
The changing of the path of a light wave while passing from one medium to another medium is called refraction. Refraction is a common phenomenon that occurs in light waves, sound waves and in water waves.
The amount of refraction is determined by the change in the speed of the light wave and the direction of the refracted wave with respect to the initial direction of the wave.
Refraction of light is a common phenomenon that occurs in our day to day life. An object submerged in water appears closer than it really is when viewed from above. This concept is behind the working of optical lenses. It is used in instruments like glasses, binoculars, cameras, microscopes, and the human eye. Some natural phenomena, like rainbows and mirages, are also due to refraction.
Laws of Refraction
Refraction is based on Snell's law. It states that for a given pair of media the ratio of the sine of the angle of incidence (θ1) to that of the sine of the angle of refraction (θ2) is equal to the ratio and is of the first media with respect to the second media. Further, it is equal to the refractive index of the first medium with respect to the second medium (n2 /n1).
The Refractive index determines the amount of bending of light. It also establishes relations among angle of incidence, angle of refraction, and the refractive index. Mathematically, for a given pair of medium refractive index is given by:
sin θ1/sin θ2 = n2/n1
State the Laws of Refraction of Light
The angle between the incident & the normal ray is called the angle of incidence 'i', and the angle between the refracted ray & normal is called the angle of refraction 'r'. The laws of refraction of light are:
The normal, the incident & the reflected ray; the entire rays lie in the same plane.
The ratio of the sine of angle of incidence & sine of angle of refraction is a constant and is called a refractive index.
The law of refraction, also called Snell's law, determines the behavior of light-rays when it passes from one medium to another medium.
Consider a ray of light incident on a plane interface between two transparent dielectric media, as shown in the figure below. According to the law of refraction, the normal, the incident ray, and the refracted ray all lie in the same plane. Also,
n1 sinθ1 = n2 sinθ2
Where,
θ1 = Angle of incidence,
θ2 = Angle of refraction.
n1 = Refractive index of 1st medium.
n2 = Refractive index of 2nd medium.
Thus, according to the law of refraction, light deviates towards the normal in an optical medium with the higher refractive index.
Note that n2>n1 in the figure.
(Image will be Updated soon)
The refractive index of a dielectric medium having dielectric constant K is represented by the formula:
n = √k
The table shows the refractive indices of some materials by using yellow light of wavelength λ = 589 nm.
Material | n |
Air (STP) | 1.00029 |
Water | 1.33 |
Ice | 1.31 |
Light flint | 1.58 |
Heavy flint | 1.65 |
Heaviest flint | 1.89 |
Diamond | 2.42 |
To Verify the Laws of Refraction of Light
(Image will be Updated soon)
The incident ray, the refracted ray & the normal all lie in one plane for a given pair of media. Also, the ratio of sine of angle of incidence to that of sine of angle of refraction is a constant.
sin i /sin r = μ
Where,
μ = Refractive index of the 2nd medium with respect to the 1st medium.
Place a rectangular glass slab on a white sheet of fixed paper on a drawing board.
Trace the boundary of the glass slab as ABCD.
Now remove the glass slab and draw a line of normal N1N2 at O.
Draw a straight line IO inclined at an angle (let say 300) with the normal. IO is the incident ray.
Fix two pins, pin P, and pin Q on the incident ray IO.
Place the glass slab within the boundary ABCD.
Fix two other pins R and S so that, when seen from the other side of slab P, Q, R, and S appear to lie in a straight line.
Remove the glass slab and the pins after marking the pinpoints P, Q, R, and S.
Join point R and S and produce the line on both sides. The ray O'E is the emergent ray.
Join OO', which is the refracted ray.
You can notice that the incident ray, the refracted ray and the normal are in the same plane. This proves the 1st law of refraction.
Let's Prove the Second Law of Refraction
Draw a circle of radius 'R' with O as the center, such that it cuts the incident and refracted rays at F and G, respectively
Draw perpendiculars from F and G to N1N2
FHO and GKO are right-angled triangles.
sin i = FH/OF
sin r = GK/OG
μ = sin i / sin r
μ = FH/OG * OG/GK
μ = FH/GK
Measure the lengths of FH and GK and write them in a table.
Do the same for different angles of incidence.
Find the ratio FH/GK for different values of incidence 'i'.
It is found that FH/GK has a set value for each observation.
This proves the laws of refraction.
How to learn Refraction?
Learning Refraction can be a little tough. It is one of the most important concepts of Physics that requires an ample amount of your time and attention. With Vedantu, you can make the learning process a lot easier. We provide you with notes on Refraction in lucid language that makes the topic easy to learn and understand. By learning Refraction from our learning platform, you can improve your chances of scoring the highest marks in your exam. Apart from this, here are some other tips to start learning the Refraction :
While studying the concept of Refraction,you should highlight or note down the important parts of the topic. You can use these notes for quick revisions during your exam preparations.
When you are learning Refraction, read the definitions and explanations thoroughly to understand the concept more clearly.
Once you are done with the textbook explanation, you can use other study materials such as revision notes and textbook solutions to improve your understanding of Refraction.
After learning the Refraction, you should try solving questions from the exercise in textbooks and reference guides to enhance your knowledge.
You can use solved examples to understand the practical part of Refraction. These examples will also give you an idea of how to solve practical questions related to refraction.
Before you try to solve the practical problems, you should go through the theoretical part of Refraction. It will help you gain more knowledge on the concept and solve the questions more easily.
Once you have a clear understanding of the Refraction, you should use sample papers and previous year physics question papers to understand the type of questions that can come in your final exam.
Try to clear all your doubts related to Refraction with your teachers before the exam to ensure you do not misunderstand any concept.
Why is it Important to Learn Refraction?
It is important to learn Refraction for all the students. By learning about refraction, you can understand the changes in speed and wavelength of length. You can also differentiate between refraction and reflection by learning the concept of Refraction. Moreover, the solved examples of Refraction provided by Vedantu will help you solve different kinds of questions based on this concept with ease. Below are some of the other reasons why you should learn Refraction:
Learning about Refraction will give you a better understanding of lenses and mirrors that are crucial concepts of physics.
Refraction - Laws of Refraction is one of the most vital parts of the Physics syllabus. So, by learning the concept of refraction, you can score significantly well in your final exam.
With Refraction, you can understand how lenses work, how a glass prism splits light into different colours, and why the water in a swimming pool always appears to be shallow.
Once you have completely understood Refraction, you will be able to solve any type of question that comes in your exam.
FAQs on Refraction in Physics: Laws and Real-World Examples
1. What is refraction of light and how does it occur when light passes from air into water?
Refraction of light is the bending of a light ray when it travels from one transparent medium to another, such as from air into water. This occurs because the speed of light changes as it enters a medium with a different optical density, causing the light to change direction at the interface between the two media.
2. State the two fundamental laws of refraction as outlined in the CBSE Physics syllabus.
The two fundamental laws of refraction are:
- The incident ray, the refracted ray, and the normal all lie in the same plane at the point of incidence.
- The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for a given pair of media, known as the refractive index (Snell’s Law).
3. How can you experimentally verify that the incident ray, refracted ray, and the normal all lie in one plane?
To verify this, place a rectangular glass slab on a sheet, trace its outline, and mark the incident ray and the normal. Pass light through the glass slab using pins for alignment. When connecting the pin points for incident and emergent rays, you'll observe that all these points lie in a single plane, confirming the first law of refraction.
4. Why is the sine function used in Snell’s Law instead of the angles themselves?
Sine values are used because the bending of light depends on the relationship between the angles and their respective sides in the triangle formed at the interface. This trigonometric relationship accurately links the incident and refracted angles with the refractive indices of the media.
5. What is the mathematical expression for the refractive index and how is it derived?
The refractive index (n) between two media is given by Snell’s Law: n1sinθ1 = n2sinθ2, where θ1 and θ2 are the angles of incidence and refraction, and n1 and n2 are the respective refractive indices. Rearranging, the refractive index (μ) can also be expressed as μ = sin i / sin r.
6. What practical applications in daily life rely on the principles of refraction?
Refraction is used in many areas including the design of eyeglasses, cameras, microscopes, and binoculars. Natural phenomena like rainbows and the appearance of a straw bent in water are also due to refraction. Understanding refraction is essential for explaining how lenses work and for recognising optical illusions such as mirages.
7. How does the refractive index affect the bending of light?
The refractive index determines how much the light will bend when entering a new medium. A higher refractive index means the light will bend more towards the normal. The greater the difference in refractive indices between the two media, the greater the deviation from the original path.
8. What is the difference between reflection and refraction of light?
In reflection, light bounces back into the same medium after striking a surface, following the law of reflection. In refraction, light passes into a different medium and bends due to a change in speed. The direction of bending depends on the relative densities of the two media.
9. Can the refractive index be less than 1? Justify your answer.
The refractive index of a material is generally greater than 1, as it compares the speed of light in vacuum to that in the medium. A value less than 1 would imply that light travels faster in the medium than in vacuum, which is not possible under normal physical conditions for transparent media.
10. Why does a submerged object appear closer to the water surface than it actually is?
This occurs because of refraction; as light travels from water (denser medium) to air (rarer medium), it bends away from the normal, causing the object to appear elevated or closer than its actual position.
11. How does the angle of incidence affect the angle of refraction in different media?
A change in the angle of incidence leads to a predictable change in the angle of refraction, as described by Snell's Law. If the refractive indices are fixed, increasing the angle of incidence increases the angle of refraction, but the relationship remains governed by the sine values of the angles.
12. What would happen if light enters a medium of the same refractive index?
If light enters a medium with the same refractive index as the originating medium, it does not bend and continues in a straight line without any deviation.
13. Why is understanding refraction crucial for mastering concepts like lenses and image formation in Physics?
Understanding refraction is essential because it is the foundational principle behind the functioning of lenses, prisms, and other optical devices. Accurate knowledge of refraction helps predict image position, magnification, and behaviour of light in various devices, all central to Physics syllabi and board exams.
14. How can practicing solved examples on refraction improve exam performance?
Practicing solved examples allows students to apply theoretical knowledge to practical board-type questions, understand problem patterns, avoid common mistakes, and enhance confidence for scoring higher marks in Physics exams as per CBSE 2025–26 requirements.
