Transcript Reflection and Refraction

Reflection and Refraction
Chapter 17
Law of Reflection
θi angle of incidence
θi angle of reflection
θi θr
Law of Reflection
θi θr
θi = θ r
Types of Reflection
Regular
Diffuse
Refraction of Light
Air(ni)
Glass(nr)
ni< nr
θi
θr
θi
θr
(Optical Density)
Air: ni
Glass: nr
ni< nr
Refraction of Light
ni
nr
θi
ni > nr
θr
ni < nr
θi
θr
ni
nr
Snell’s Law
ni
nr
θi
θr
ni sin θi = nr sin θr
A ray of light has an angle of
incidence of 25.0 upon 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
-1
sin (sin
θi /nr )= θr
-1
sin (sin
25° /1.54)= θr
θ = 17 °
Speed of Light and
The Index of Refraction
c
n= v
n
n: index of refraction
c: speed of light in a vacuum
v: speed of light in material
What is the speed of light in
diamond?
Find: vD
Given: nD = 2.42
8
c = 3.0 X 10 m/s
Equation: vD = c/nD
8
vD = 3.0 X 10 m/s / 2.42
vD = 1.2 X
8
10 m/s
Total Internal Reflection
Total Internal Reflection
n1
n2
n2 > n1
Total Internal Reflection
Critical
Angle
θc
n2 > n1
90º
n1
n2
Total Internal Reflection
ni sin θi = nr sin θr
ni sin θc = nr sin 90º
ni sin θc = nr (1)
nr
sin θc = n
i
Total Internal Reflection
θc =
n
-1
sin r
ni
Example: What is the critical
angle between water and air?
Given: nw = 1.33
na = 1.00
n
r
-1
Given: θc = sin n
i
1.00
-1
θc = sin 1.33
θc = 49°
Mirage
Diamonds (n = 2.42)
Fiber Optics
Dispersion cause by Refraction
Prism
Prism
The 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