Reflection and Refraction

Chapter 17

Law of Reflection

θi θr

θi angle of incidence

θi angle of reflection

Law of Reflection

θi θr

θi = θr

Types of Reflection

Regular Diffuse

Refraction of Light

θr

θi

θi

θr

Air(ni)

Glass(nr)

ni< nr

Index of Refraction n(Optical Density)

Air: ni

Glass: nr

ni< nr

Refraction of Light

θr

θini

nr

ni < nr

ninrθr

θi

ni > nr

Snell’s Law

θr

θini

nr

ni sin θi = nr sin θr

A ray of light has an angle of incidence of 25.0upon the surface of a piece of quartz. What is the angle of refraction?θi

θr

Air: ni = 1.00

Quartz: nr = 1.54

Given: ni = 1.00 nr = 1.54 θi = 25°

Find: θr

Equation: nisin θi = nrsin θr

sin-1(sin θi /nr )= θr

sin-1(sin 25° /1.54)= θr

θr = 17 °

Speed of Light andThe Index of Refraction

nn = c v

n: index of refractionc: speed of light in a vacuumv: speed of light in material

What is the speed of light in diamond?

Given: nD = 2.42 c = 3.0 X 108m/s

Equation: vD = c/nD vD = 3.0 X 108m/s / 2.42

vD = 1.2 X 108m/s

Find: vD

Total Internal Reflection

Total Internal Reflection

n1

n2

n2 > n1

Total Internal Reflection

n1

n2

n2 > n1

Critical Angle

90º

θc

Total Internal Reflection

ni sin θi = nr sin θr

ni sin θc = nr sin 90º

ni sin θc = nr (1)

sin θc = ni

nr

Total Internal Reflection

θc = sin-1 ni

nr

Example: What is the critical angle between water and air?

Given: nw = 1.33 na = 1.00

Given: θc = sin-1 ni

nr

θc = sin-1 1.331.00

θc = 49°

Mirage

Diamonds (n = 2.42)

Fiber Optics

Dispersion cause by Refraction

Prism

PrismThe amount that light is diffracted depends on its wavelength. Shorter

wavelengths are bent more than longer wavelengths. Violet is

bent more than Red!!!

Rainbow

Spectroscopy