Post on 17-Jan-2016
transcript
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