Table of contents | |
What is Total Internal Reflection? | |
Formula of Total Internal Reflection | |
Applications of Total Internal Reflection | |
Important Questions for Exam |
Have you ever noticed, how beautifully a diamond shines? It seems like light rays are stuck inside the structure of the diamond and getting reflected continuously. This is an application of Total Internal Reflection, which we are going to study about in detail in this document.
When a light ray travelling from a denser medium towards a rarer medium is incident at the interface at an angle of incidence greater than the critical angle, then light rays get reflected back into the denser medium. This phenomenon is called Total Internal Reflection.
Total Internal Reflection
The following are the two conditions of total internal reflection:
Note: The critical angle increases with temperature.
1 Crore+ students have signed up on EduRev. Have you? Download the App |
Total Internal Reflection:
Critical Angle, θ: sinθ = n2/n1 (n1 > n2)
Test: Total Internal Reflection
|
Start Test |
Applications of Total Internal Reflection
➢ Optical Fibre
➢ Diamond
➢ Mirage
Example.1: An optical fibre made up of glass with a refractive index of n1 = 1.5 which is surrounded by another glass with refractive index n2. Find the refractive index n2 of the cladding such that the critical angle between the two cladding is 80°.
Solution.
Critical angle, θ = 80°
Refractive index, n1 = 1.5
Refractive index n2 =?
Using the below formula, we can calculate n2:
sinθ = n2/n1
sin80∘ = (n2 / 1.5)
n2 = 1.5 * sin80∘
n2 = 1.48
Example.2: Find the refractive index of the medium whose critical angle is 40°.
Solution.
Critical angle, θ = 40°
The refractive index of the medium, μ =?
μ = 1/sinθ
μ = 1/sin40∘
μ =1/0.65
µ = 1.6
Example.3: Which of the following is an example of total internal reflection?
1. Mirror
2. Twinkling of stars
3. Mirage
4. Thin film of soap bubble
Answer: Option 3: Mirage
Explanation: Mirage is an example of total internal reflection.On hot summer days, the air near the ground becomes hotter than the air at higher levels. Due to this, there is a difference in the refractive index of the air in different layers.
Example.4: A scuba diver is wearing a head lamp and looking up at the surface of the water. If the minimum angle to the vertical resulting in total internal reflection is 25∘, what is the index of refraction of the water?
θair=1
a) 2.37
b) 0.85
c) 0.49
d) 1.12
Answer: 2.37
Solution:
Example 5: A ray of light makes a transition from a sample of benzene to water. What is the minimum angle the light must make with respect the normal in order for the light to be completely reflected back into the sample of benzene? The index of refraction for water is 1.33 and for benzene is 1.50.
Solution:
289 videos|635 docs|179 tests
|
1. What is Total Internal Reflection? |
2. What is the formula for Total Internal Reflection? |
3. What are the applications of Total Internal Reflection? |
4. What are some important questions related to Total Internal Reflection? |
5. How is Total Internal Reflection relevant to the NEET exam? |
|
Explore Courses for JEE exam
|