Page 181 - Physics_Form_2
P. 181
Refraction and dispersion of light
Exercise 5.1 (a) Speed of light in diamond.
1. A coin is at the bottom of a trough (b) The critical angle for diamond.
containing three immiscible liquids 7. The critical angle for a beam of
of refractive indices 1.3, 1.4 and light travelling between water and
1.5, poured one above the other at air is 49°.
FOR ONLINE READING ONLY
heights 30 cm, 16 cm, and 20 cm, (a) A beam strikes the/boundary
respectively. What is the apparent between water and air and
depth at which the coin appears undergoes total internal
when observed from an air medium reflection. Will the beam stay
outside? In which medium will the in the air or the water? Explain.
coin be seen? (b) Explain what happens when a
2. Light is incident on an air-water beam of light from the air strikes
interface at an angle of 40°. Given the surface of a calm lake at an
that the refractive index of water angle of 50° from the normal.
is 1.33, determine the angle of
refraction of the light in the water. Refraction of light by a triangular glass
3. A stone is lying at the bottom of a prism
pool of water 3 m deep. What would A triangular glass prism is a transparent
be the stone’s depth as seen by an object having two triangular and three
observer standing near the pool? Use rectangular faces. The refraction of light
η =1.30. by a triangular glass prism is different
w
4. (a) The speed of light in water from the refraction by a rectangular glass
and air is 2.8 10 m/s 8 and prism. For a triangular glass prism, the
3.0 10 m/s 8 , respectively. emergent ray of light is not parallel to
Determine the refractive index the incident ray of light. This is because,
from air to water. when a ray of light enters the glass prism,
(b) A ray of light travelling from it gets deviated two times. First, light is
air to water is incident at the refracted when it enters the glass prism
surface of water at an angle and then refracted for the second time
of 30°. Calculate the angle of when it comes out of the prism as shown
refraction in the water. in Figure 5.11. This is possible because
5. A swimming pool appears to be 1.5 the refracting surfaces of the prism are
m deep. If the refractive index of not parallel to each other, therefore when
water is 1.3, determine the real depth the ray of light passes through the prism
of the pool. it bends towards the normal, which is
6. Diamond has a refractive index oriented towards the prism’s base. The
of 2.42. Given that the speed of amount by which light bends is dependent
light in a vacuum is 3.0 10 m/s 8 on the angle of incidence, the wavelength
, determine: of the light, and the refractive indices of
the materials through which light travels.
175
Physics Form 2 Final.indd 175 25/10/2025 10:28
