Page 241 - text book form physics kssm 2020

Chapter 6
Light and Optics
Based on Figure 6.5, the value of n sin θ is the same as n sin θ for the three different
2
1
1
2
mediums. According to the law of refraction of light, when light travels from one medium
to another:
• The incident ray, refracted ray and normal meet at one point and are in the same plane.
• Snell’s Law: n sin θ = n sin θ 2 , where n = refractive index of medium 1
1
2
1
1
2
n sin θ 1 n = refractive index of medium 2
2 = θ = angle of incidence in medium 1
1
n 1 sin θ 2 θ = angle of refraction in medium 2
2

Normal Normal
Incident ray
Medium 1 Air
(n )
1 (n = 1)
When medium 1 is air (n 1 = 1) θ 1 Point of incidence i
and medium 2, n 2 = n
sin i
n = Medium 2 Medium
sin r (n ) r (n)
i is the angle of incidence in air, θ 2 2
r is the angle of refraction in
sin i
medium 2 Refracted ray n = ––––
sin r

Figure 6.6 Law of refraction of light

Observe Figure 6.7. Why does Angle of refraction depends
light ray bend when entering a on the angle of incidence
glass block? and the value of refractive Air
index of the glass block.

Glass
block
Air

Figure 6.7 Bending of light ray

235
6.1.3
6.1.3 6.1.4 235
6.1.4