Lecture 6
> Optics
> Reflection & Refraction
Giancoli, Physics 6/eSerway & Vuille, College Physics 8/eSerway & Jewett, Physics for Scientists & Engineers, 6/eTippens, Physics 7/eYoung, Freedman & Ford, University Physics 14/e
1Villacorta--DLSUM-SCITECS-L06-1718Term03
Ray Optics
2
> Light travels in straight lines
> Light propagation can be illustrated using rays, showing their direction as it travels through space.
> Geometric optics refers to studying light propagation using the rays and angles
Villacorta--DLSUM-SCITECS-L06-1718Term03
Reflection
3
> Shiny objects reflect light that hits it
> Angle of incidence, angle of reflection + Light bounces back at the same angle that it hit the object + Optical plane + Surface normal + Law of reflection
> Types of reflections + Diffuse: scattered, uneven, rough surface + Specular: mirror, image formation
> Images: plane mirrors + Virtual image: can't be projected + Real image: can be projected
Villacorta--DLSUM-SCITECS-L06-1718Term03Johan Arveliushttps://en.wikipedia.org/wiki/File:Reflection_angles.svg
Refraction
4
> Light travels slower through a medium than through vacuum: the ratio of these speeds is the index of refraction of the material
n=c
v
boomeria.org
Villacorta--DLSUM-SCITECS-L06-1718Term03 https://en.wikipedia.org/wiki/File:Snells_law.svg
Refraction contd.
5
> When light passes through a material, it bends due to traveling at a different speed: the relationship is given by Snell's law
Willebrord Snellius1580-1626
wikipedia.orgagilescientific.com
n1 sin θ1=n2 sin θ2
Villacorta--DLSUM-SCITECS-L06-1718Term03
Total Internal Reflection
6
> When light goes from a slow medium to a fast one, it is possible for the light to be reflected inward and NOT refract into the second faster medium.
> This occurs at a given critical angle θC
for material
> Fiber optic cables work in this manner.
ualberta.caVillacorta--DLSUM-SCITECS-L06-1718Term03
Ray Tracing
7
> Images are formed by light rays intersecting + Real image: intersection of reflected or refracted light rays + Virtual images: intersection of the projections of reflected or refracted light rays
> The place where the image will form is the image distance: + It can be farther + or nearer to the mirror or lens
> The image can also be: + Magnified + or shrunk
Villacorta--DLSUM-SCITECS-L06-1718Term03
Mirrors
8
> The principal axis goes through the center of the mirror.
> The center represents the center of a circle that the mirror is part of.
> The focus is approximately located halfway between the center and the mirror.
langlopress.net
> Light rays passing through the center bounce off the mirror, passing through the center again.
> Light rays passing through the focus bounce off the mirror, parallel to the principal axis.
> Light rays initially parallel to the principal axis bounce off the mirror passing through the focus.
Villacorta--DLSUM-SCITECS-L06-1718Term03
Mirrors contd.
9
* q > 0 if the reflected or refracted rays are on the same side as the focus
* q < 0 if the reflected or refracted rays are on the opposite side as the focus
langlopress.net
1
p+
1
q=
1
f
m=image ht
object ht=
�q
s
Villacorta--DLSUM-SCITECS-L06-1718Term03
Mirrors contd.
10
* q > 0 if the reflected or refracted rays are on the same side as the focus
* q < 0 if the reflected or refracted rays are on the opposite side as the focus
langlopress.net
1
p+
1
q=
1
f
m=image ht
object ht=
�q
s
Villacorta--DLSUM-SCITECS-L06-1718Term03
Summary
11
> Light travels in straight lines
> Light can be reflected off a surface or refracted through a medium
Mirrors can make images from light rays that bounce off it
Villacorta--DLSUM-SCITECS-L06-1718Term03
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