refraction and reflction

ReflectionReview

NORMAL LINE

PERPENDICULAR

INCIDENCE

INCIDENT

40 ͦ� ͦ ͦ ͦ ͦ ͦ ͦ ͦ ͦ

REFLECTION

REFLECTED

Slide ͦ4 ͦ

Law of Reflection

qi = qr

Refraction

The change in direction of a wave as it crosses the boundary between two media in which the wave travels at different speeds.

Index of Refraction

materialinlightofspeed

vacuuminlightofspeedn

Index of RefractionMaterial Index of RefractionVacuum 1.0000

Air 1.0003Ice 1.3100

Water 1.3330Ethyl Alcohol 1.3600

Plexiglas 1.5100Crown Glass 1.5200

Light Flint Glass 1.5800Dense Flint Glass 1.6600

Zircon 1.9230Diamond 2.4170

Rutile 2.9070Gallium phosphide 3.5000

Index of refraction of air

Speed of light In vacuum 299, 792 km/sIn air 299,705 km/s

n= 299, 792 km/s / 299, 705 =1.0003

Index of refraction of waterSpeed of light

In vacuum 299, 792 km/sIn water 224, 900 km/s

n= 299, 792 km/s / 224, 900 =1.3330

Snell’s Law

2211 sinsin nn

ExampleLight travels from air into an optical fiber with an

index of refraction of 1.44.  (a) If the angle of incidence on the end of the fiber is 22o, what is the angle of refraction inside the fiber?

n1 = 1.00

n2 = 1.44

θ1 = 22o

(1.00) sin 22o = 1.44 sin θ2. 

(1.00/1.44) sin 22o = sin θ2

0.260 = sin θ2

sin-1 (0.260) = θ2 

 15o= θ2 

2211 sinsin nn

Worksheet

Label the following diagramAngle of Incidence

Incident Ray

Normal Line

Refracted Ray

Angle of Refraction

n= 299, 792 km/s / 169, 500 km/s =1.76

Substance Speed of Light in

Substance

Refractive Index

Sapphire 169,500 km/s 1.76

1.36 sin45 o = 2.42 sin θ2. (1.36/2.42) sin 45o = sin θ2

0.40 = sin θ2

sin-1 (0.40) = θ2  23.58o= θ2 

45 ͦ�

24 ͦ�

Water:1.00 sin40 o = 1.33 sin θ2. (1.00/1.33) sin 40o = sin θ2

0.40 = sin θ2

sin-1 (0.40) = θ2  28.90o= θ2 

Perspex:1.00 sin40 o = 1.5 sin θ2. (1.00/1.5) sin 40o = sin θ2

0.40 = sin θ2

sin-1 (0.40) = θ2  25.37o= θ2 

Angle of Incidence (in air)

Angle of refraction in water (nwater = 1.33)

Angle of refraction in perspex (nperspex = 1.5)

40 � 28.90 25.37

Which arrow point the real position of the fish and which arrow point the position of the fish’ image (from the man’s position?)