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Question
The refractive index of air with respect to glass is expressed as `""_g μ_a=sin i /sin r`.
- Write down a similar expression for aμg in terms of the angles i and r.
- If angle r = 90°, what is the corresponding angle i called?
- What is the physical significance of the angle i in part (b)?
Solution
- R.I of glass w.r.t. air `= ""_aμ_g = sini/sinr`
∠r is angle of incidence in air
∠i is angle of refraction in medium - When angle r = 90°
∴ sin 90° = 1 in air
Angle i in medium is called the critical angle. - The significance of ∠i = ic = critical angle is:
The refractive index of the denser medium relative to the rarer medium can be computed using the critical angle value.
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