Page 186 - Physics_Form_2

Physics for Secondary Schools

Table 5.3 (b) Explain why a rectangular glass
Prism angle, A block does not cause dispersion
Angle of Angle of of light.
incidence ()i deviation ()D 2. Light travelling through transparent

25 oil enters a glass with a refractive
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30 index of 1.5. If the refractive index
35 of glass with respect to the oil is
40 1.25, what is the refractive index of
the oil?
45 3. A monochromatic light is incident on
50 an equilateral glass prism at an angle
55 of 30 and emerges at an angle of
0
60 75º. What is the angle of deviation
produced by the prism?
Questions 4. A light ray falls at normal incidence
(a) When light passes through a on the first face of an equilateral prism
triangular glass prism, what happens such that, the angle of incidence is
to the angle of deviation when the 45 , and emerges from the second
0
angle of incidence changes? face by making the same angle with
(b) Does the angle of minimum deviation the normal. What is the refractive
(Dm) change when a different prism index of the material of the prism?
is used?
5. The angle of minimum deviation
for a prism is 37º. If the angle of
The angle of deviation first decreases the prism is 60º, find the refractive
to attain the minimum value of Dm and
then increases as the angle of incidence index of the material of the prism.
increases. The angle of minimum deviation 6. A rectangular glass block of thickness
is important for calculating the refractive 10 cm and refractive index 1.5 is
index of materials, using the equation: placed over a small coin. A beaker

⎛ A + D m ⎟ ⎞ filled with water of refraction index
⎜
sin⎜ ⎟ ⎟ 4/3 to the height of 10 cm is placed
sini ⎜ ⎜ 2 ⎟ ⎠
⎝
η = = over the block.
sinr sin A (a) Find the apparent position of the
2 coin when viewed normally.
(b) If the eye is slowly moved
Exercise 5.2 away from the normal, then at
1. (a) Describe the angle of minimum a certain position the object is
deviation in a triangular glass found to disappear due to total
prism and its relationship with internal reflection. At what
the angle of incidence and the surface does it happen and why?
prism’s angle.

180
Student’s Book Form Two

Physics Form 2 Final.indd 180 25/10/2025 10:28