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Question
Trace a ray of light incident at 30° on a surface if travelling from glass to air. What is the angle of refraction in this case? (R.I. for glass = 3/2).
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Solution
For a ray of light from glass to air R.I. is denoted as gμa.
`""_"g"mu_"a"=1/(""_"a"mu_"g")`
∴ `sin"i"/sin"r′"=1/(""_"a"mu_"g")`
sin r′ = aμg × sin i
and aμg = `3/2`
∴ sin r′ = `3/2xx1/2`
= `3/4`
= 0.7500
∴ r′ = 48°36′
Angle of refraction for glass to air = 48°36′.
RELATED QUESTIONS
After tracing the path of a ray of light passing through a rectangular glass slab for four different values of the angle of incidence, a student reported his observations in tabular form as given below:
| S.No | ∠ i | ∠ r | ∠ e |
| I | 30° | 19° | 29° |
| II | 40° | 28° | 40° |
| III | 50° | 36° | 50° |
| IV | 60° | 40° | 59° |
The best observation is
(A) I
(B) II
(C) III
(D) IV
Select from the following the best experimental setup for tracing the path of a ray of light passing through a rectangular glass slab.
(a) P
(b) Q
(c) R
(d) S
The critical angle for glass-air is 45° for the light of yellow colour. State whether it will be less than, equal to, or more than 45° for (i) ref light, (ii) blue light?
Draw ray of light bending towards the normal while passing from air to glass. Label your diagrams.
The figure shows two prisms A and B. A monochromatic ray of light PO is incident at the face of the prism A. Complete the diagram to show the path of the ray till it emerges out of the prism B.
In the diagram alongside a ray of light, PQ is incident normally on one face AB of an equilateral glass prism. What is the angle of incidence at the faces AB and AC?
Write the approximate values of speed of light in (i) air and (ii) glass. Use these values to calculate the refractive index of glass with respect to air.
