Reflectionvs.Refraction
Refraction
zRefraction of Light: Bend orchange direction
z1. As light rays enter a newmedium the cause light to bend
z2. The denser the medium –the slower the light travels
z3. Index of Refraction: ameasure of how much amedium bends the light thattravels through it.
z4. The faster the beam, it willbend away from normal, theslower the beam, it will bendtoward the normal.
zA mirage is a visual distortion produced bythe refraction of light.
zSome mirages produce a mirror or a wateryimage, and others may make an objectappear larger or smaller, nearer or furtheraway.
The ray model says…
Light has four different ways inwhich it can interact with matter.
Medium 1
Medium 2
Reflection
Light has four different ways inwhich it can interact with matter.
Medium 1
Medium 2
Refraction
Light has four different ways inwhich it can interact with matter.
Medium 1
Medium 2
Scattering
Light has four different ways inwhich it can interact with matter.
Medium 1
Medium 2
Absorption
Reflective Objects
Reflection
Reflection off Paper
Reflection off aMirror
Regular Reflection
Diffuse Reflection
Law of Reflection
Normal - an imaginaryline drawn perpendicularto the surface
Reflections in a Mirror
Q
An observer observes a light source S in a mirror.Where does he perceive the mirror image of S tobe located?
S
●1
●2
●3
●4
How big does a mirror have to be inorder to see your entire length in it?
Half His Height!
To see more of her head in the mirror, she …
1. should hold the mirror closer
2. should hold the mirror farther away
3. needs a bigger mirror
Refraction
i
R
Refraction
As light travelsfrom one mediumto another, thespeed of lightchanges and thelight bendsaccordingly.
n1 sin I = n2 sinR
Snell’s Law: The Law of Refraction
Index of Refraction ofthe media in which theangle of incidence is
Index of Refraction ofthe media in which theangle of refraction is
Index of Refraction
Cannot be less than 1.00
Air = 1.00
Glass = 1.5
Water = 1.33
Q
Bruno wishes to “spear” a fish with a laser. Should heaim the laser beam…
1.above 2. below 3. directly at
the observed fish to make a direct hit?
Light is incident on a block of glass asshown. Which ray is the refracted ray?
1.
2.
3.
4.
Calculate the critical angle θ from glass(n=1.5) to air.
θ
1.52.9o 2. 41.8o 3. 32.2o
4. 22.5o 5. 12.3o
Calculate the critical angle θ from glass(n=1.5) to air.
θ
1.52.9o 2. 41.8o 3. 32.2o
4. 22.5o 5. 12.3o
n1 sin I = n2 sinR
1.5 sin I = 1.0 sin 90
sin I = .667
I = 41.8
Fiber Optics
Fiber optics uses totalinternal reflection
