70
n
c
v
=
Where
n = index of refraction
c = speed of light in vacuum
v = speed of light in medium
2.5.6 Snell’s Law
Snell’s law or law of refraction relates to the refractive indices of two different
materials with the angles of reflection and refraction as:
n
n
1
2
2
1
=
sin
sin
θ
θ
or
n
n
1
1
2
2
sin
sin
θ
θ
=
Where
n 1  = refractive index of material 1
n 2  = refractive index of material 2
θ 1  = angle of incident light ray in material 1
θ 2  = angle of refracted light ray in material 2
θ 2 =90
o
θ 1 =θ c
n 2
n 1
Rarer medium
Denser medium
n 1 >n 2
Fig. 2.11 Illustration of
critical angle
2 Fundamentals of Physics for Environmental and Medical Professionals