Page 215 - Physics_Form_2

Refraction and dispersion of light

2. A rectangular glass block 5 cm thick is placed on top of the page of a book. If
the refractive index of the glass block is 1.53, calculate the apparent depth of the
letters on the book.
3. A ray of light is incident at an angle of 60° on a block of glass of refractive index
1.5. Determine the angle of refraction of the ray.
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4. A small coin was placed at the bottom of a tall glass containing some water and
viewed from above. The real and apparent depths of the coin were then measured.
By varying the depth of the water in the jar, the following readings were obtained:

Table 5.7
Real depth (cm) 8.1 12.0 16.0 20.0
Apparent depth (cm) 5.9 9.0 12.0 15.1

By plotting an appropriate graph from the results, determine the refractive index
of the water.
5. State whether it is possible or not to obtain a critical angle when light travels from:
(a) air to glass. (c) glass to air.
(b) water to air. (d) air to water.

6. The refractive index of water is 1.33 and that of glass is 1.5. Calculate the critical
angle for:
(a) a glass-air interface (b) a water-air interface (c) a glass–water interface
7. Figure 5.46 shows some objects placed in front of or behind lenses.

2F F F 2F 2F F F 2F

(a) (b)

2F F F 2F 2F F F 2F

(c) (d)
Figure 5.46

By construction, find the nature and position of the image formed by each object.

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Physics Form 2 Final.indd 209 25/10/2025 10:28