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Question
The refractive index of glass is 1.5. From a point P inside a glass block, draw rays PA, PB and PC incident on the glass air surface at an angle of incidence 30°, 42° and 60° respectively.
- In the diagram show the approximate direction of these rays as they emerge out of the block.
- What is the angle of refraction for the ray PB?
`("Take" sin 42° =2/3)`
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Solution
- A diagram with rays PA, PB and PC is shown below:
- Given, μ = 1.5
As we know,
`sin i_c = 1/mu`
substituting the values in the formula, we get,
`sin i_c = 1/1.5`
sin ic = 0.667
ic = 41.8
Hence, we can round off ic = 42°
Applying `sin r/sin i = ""_amu_g`
sin r = `""_amu_g xx sin i`
sin r = `""_amu_g xx sin 42°`
Given, sin 42° = `2/3`
and `""_amu_g = 3/2`
substituting the value in the formula, we get,
`sin r = 3/2 xx 2/3`
sin r = 1
As sin r = 1, the angle of refraction is 90°.
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