Refraction of Light
Snell’s Law
• Taking the results from your lab we find
using the y = m x + b format, we get
Snell’s Law
y=mx+b
Sin i = 1.5 (sin r) + 0
sin i = (index of refraction) sin r +0
• The index of refraction is signified by the
letter ‘n’
Snell’s Law
• So we get the equation
Sin i = n (Sin r)
• Add to it the index of refraction of the
material you started in we get
Snell’s Law
n1 (sin θ1) = n2 (sin θ2)
Snell’s Law
n1 (sin θ1) = n2 (sin θ2)
This equation is called the
Snell’s Law Equation
Snell’s Law
n1 (sin θ1) = n2 (sin θ2)
This represents the material you
are in
θ1
n1
n2
θ2
Snell’s Law
n1 (sin θ1) = n2 (sin θ2)
This represents the material you
are going into
θ1
n1
n2
θ2
Refraction of Light
• As light enters different mediums, it bends
differently
Refraction of Light
• As light enters different mediums, it bends
differently
Refraction of Light
• Every transparent material has its own
index of refraction.
Air = 1.0
water = 1.33
glass = 1.5
diamond = 2.42
Refraction of Light
• What does the index of refraction number
actually mean?
Refraction of Light
• What does the index of refraction number
actually mean
• It tells how much slower the speed of light
is in that material, rather than in a vacuum
Refraction of Light
• So in water (n=1.33), the speed of light in
water is
Speed of light 3 x 10^8
=
= 2.3 x 10^8 m/s
in water
1.33
Refraction of Light
• As light goes from a low index (air) to a
higher index (water), the light slows and
bends towards the normal.
Refraction of light
• Just opposite occurs if we go from a high
index (water) to a low index (air). Light
speeds up and bends away from the
normal
Refraction of Light
• Example Problem
A ray of light enters water at an angle of 25
degrees. What is the angle of refraction?
Refraction of Light
• Example Problem
A ray of light enters water at an angle of 25
degrees. What is the angle of refraction?
n1= 1
θ1 = 25 degrees
n2 = 1.33
θ2 = ?
Refraction of Light
• Example Problem
A ray of light enters water at an angle of 25
degrees. What is the angle of refraction?
n1(sin θ1) = n2(sin θ2)
1(sin 25) = 1.33 (sin θ2)
θ2 = 18.5 degrees
Homework
• Do worksheet 1 in minipacket (both sides)