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Physics Lesson 12.3.7 - Total Internal Reflection
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Welcome to our Physics lesson on Total Internal Reflection, this is the seventh lesson of our suite of physics lessons covering the topic of Refraction of Light, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.
Total Internal Reflection
When the angle of incidence is greater than the critical angle, the light ray is reflected back into the first medium after touching the interface between the two media. This means the interface acts like a plane mirror. As a result, a phenomenon known as total internal reflection does occur. During this process, the laws of reflection are applied. However, you can also use the laws of refraction to study this process by considering the refraction angle greater than 900 as shown in the figure.
The ray 3 is incident at a larger angle than the critical. As a result, it is reflected back into the first medium. The angle of refraction is r3 while the angle of reflection is the supplementary of r3 (1800 - r3).
Example 4
A light ray moves out from glass to air at 500 to the normal line.
- What phenomenon does occur in this case?
- What is the refraction angle?
Take the critical angle of glass-to-air equal to 41.80.
Solution 4
- Since the angle of incidence is greater than the critical angle, a total internal reflection will take place. Therefore, the angle of reflection will be equal to the angle of incidence, i.e. 500.
- The angle of refraction is the supplementary of the angle of total internal reflection, i.e. 1800 - 500 = 1300 as shown in the figure below.
A practical application of total internal reflection is the submarine. It cannot be detected from above the water as it emits light at angles that are greater than the critical angle of water-to-air (41.80).
You have reached the end of Physics lesson 12.3.7 Total Internal Reflection. There are 7 lessons in this physics tutorial covering Refraction of Light, you can access all the lessons from this tutorial below.
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