Edexcel IGCSE Physics 3.21 Critical angle
Practise defining critical angle, reading it from ray diagrams, and predicting whether light refracts out or undergoes total internal reflection.
- Syllabus
- First assessment 2019
- Course
- Physics 4PH1
Exam points
- determine the critical angle from a prism ray diagram using the boundary geometry
- explain c as the incident angle in the denser medium giving refraction at 90°
- predict whether a ray refracts out or totally internally reflects for a given c
3.21 Critical angle question 1
[Maximum number: 2]
This question is about refraction.
The torch is moved below the surface of the water. Light from the torch is incident on the water surface at an angle greater than the critical angle.
Explain the meaning of the term critical angle.
You may draw a diagram to help your answer.
the angle of incidence (in the slower medium); above which gives total internal reflection OR gives an angle of refraction of 90^;
allow ideas if clear from diagram
allow TIR for total internal reflection
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