Refraction

1
Refraction

• The travel of light from one medium to another.
• Change in wave speed
• change in wavelength
• Change in direction
• No change in frequency

2
REFRACTION
N
li gt lr
incident ray
fi fr
Qi
fast
slow
bends toward Normal
Qr
refracted ray
3
REFRACTION
N
li lt lr
incident ray
fi fr
Qi
slow
fast
Qr
bends away from Normal
refracted ray
4
Fast to Slow
Slow to Fast
N
Qi
Qi
fast
slow
slow
fast
Qr
refracted ray bends toward N
refracted ray bends away from N
Qr
5
Index of Refraction (n)
(speed of light in vacuum)
(speed of light in a given medium)
The bigger the n value, the slower the light
travels.
6
Index of Refraction (n)

• MATERIAL n
• AIR 1.0003
• WATER 1.3
• GLASS 1.5
• DIAMOND 2.4

7
SNELLS LAW
N
sin Q1 l1/hyp
V1ltV2
sin Q2 l2/hyp
Q1
V1
medium 1
Q1
Q1
hyp
Q2
medium2
Q2
Q2
V f l
V2
f1 f2
V a l
8
Snells Law
n2


n1
n1 sin Q1 n2 sin Q2
9
Critical Angle (Qc)
Qi
Qi
Qc
glass
air
Qr 90
Qr
Qr
If the incident angle is equal to the critical
angle, the refracted angle 90
10
Total Internal Reflection
reflected ray
QigtQc
glass
air
If the incident angle is greater than the
critical angle, the boundary behaves like a
perfect mirror.
11
Total Internal Reflection
n1 sin Q1 n2 sin Q2
(slow medium)
(fast medium)
If material 2 is air, n2 1
If Q1 Qc Then Q2 90
n1 sin Qc 1 sin 90 1
12
Dispersion
different wavelengths slowed down to different
speeds
N
rainbow
white light
prism
13
(No Transcript)
14
RAINBOWS
raindrop
white light
15
fish tank