Edexcel IGCSE Physics 3.22 Critical angle equation
Practise using sin c = 1/n to calculate critical angle or refractive index, with correct rearrangement, rounding and degree notation.
- Syllabus
- First assessment 2019
- Course
- Physics 4PH1
Exam points
- state or rearrange sin c = 1/n for critical angle and refractive index questions
- calculate c from a given refractive index using sin^-1 and give the angle in degrees
- calculate n from a given critical angle, keeping suitable significant figures
3.22 Critical angle equation question 1
[Maximum number: 4]
This question is about refraction.
Question (a)
(a)
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.
[ 4 ]
Question (i)
(i)
State the formula linking critical angle and refractive index.
[ 1 ]
sin c = 1 / n
Accept:
- rearrangements and mixture of symbols and words
Question (ii)
(ii)
Calculate the critical angle of water.
Assume the refractive index of water is 1.3
[ 3 ]
- substitution
- rearrangement
- evaluation
Example:
- sin c = 1 / 1.3
- c = sin^-1(1 / 1.3)
- c = 50 degrees
Accept:
- 50.3
- 50.28...
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