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Total Internal Reflection, Brewster's Angle, Dispersion, and Lenses in Physics 1161, Exams of Physics

A series of slides from a university physics lecture covering topics such as total internal reflection, brewster's angle, dispersion, and lenses. The slides include explanations, diagrams, and questions for students. The lecture material is based on sections 26-5 to 27-3 of the textbook.

Typology: Exams

Pre 2010

Uploaded on 08/18/2009

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Physics 1161: Lecture 18, Slide 1
Total Internal Reflection, Brewster’s
Angle, Dispersion, Lenses
Today’s Lecture will cover textbook
sections 26-5 – 26-7
Physics 1161: Lecture 18
Exam
III
Physics 1161: Lecture 18, Slide 2
Total Internal Reflection
normal
θ
2
θ
1
n
2
n
1
Recall Snell’s Law: n
1
sin(θ
1
)= n
2
sin(θ
2
)
(n
1
> n
2
θ
2
> θ
1
)
θ
1
= sin
-1
(n
2
/n
1
) then θ
2
= 90
θ
c
Light incident at a larger angle will
only have reflection (θ
i
= θ
r
)
θ
i
θ
r
“critical angle”
Physics 1161: Lecture 18, Slide 3
Can the person standing on the edge of the pool be
prevented from seeing the light by total internal reflection ?
1) Yes 2) No
Preflight 18.1
pf3
pf4
pf5

Partial preview of the text

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Physics 1161: Lecture 18, Slide 1

Total Internal Reflection, Brewster’s

Angle, Dispersion, Lenses

• Today’s Lecture will cover textbook

sections 26-5 – 26-

Physics 1161: Lecture 18 Exam

III

Physics 1161: Lecture 18, Slide 2

Total Internal Reflection

normal

θ 2

θ 1

n 2

n 1

Recall Snell’s Law: n 1 sin(θ 1 )= n 2 sin(θ 2 )

(n 1 > n 2 ⇒ θ 2 > θ 1 )

θ 1 = sin-1(n 2 /n 1 ) then θ 2 = 90

θc

Light incident at a larger angle will only have reflection (θi = θr)

θi^ θr

“critical angle”

Physics 1161: Lecture 18, Slide 3

Can the person standing on the edge of the pool be prevented from seeing the light by total internal reflection?

  1. Yes 2) No

Preflight 18.

Physics 1161: Lecture 18, Slide 4

ACT: Refraction

• As we pour more water into bucket, what

will happen to the number of people who

can see the ball?

1) Increase 2) Same 3) Decrease

Physics 1161: Lecture 18, Slide 5

Fiber Optics

At each contact w/ the glass air interface, if the light hits at greater than the critical angle, it undergoes total internal reflection and stays in the fiber.

We can be certain that ncladding < ninside

ninside

Add “cladding” so outside material doesn’t matter!

ncladding

noutside

Physics 1161: Lecture 18, Slide 6

Brewster’s angle

…when angle between reflected beam and refracted beam is exactly 90 degrees, reflected beam is 100% horizontally polarized!

Reflected light is partially polarized (more horizontal than vertical). But…

horiz. and vert. polarized

θθ θθB θθθθB

90º-θθθθB

horiz. polarized only! n^1 n 2

tan θB =

Physics 1161: Lecture 18, Slide 10

Preflight 18.

Wow look at the variation in index of refraction!

Where is red? Where is blue?

Physics 1161: Lecture 18, Slide 11

Flat Lens (Window)

n 2 n 1

Incident ray is displaced, but its

direction is not changed.

←t→

θθ θθ 1 θθ θθ 1

If θθθθ 1 is not large, and if t is

small, the displacement, d,

will be quite small.

d

Physics 1161: Lecture 18, Slide 12

Converging Lens

All rays parallel to principal axis pass through focal point F. (^) Double Convex

P.A.

Preflight 18.6 F

A beacon in a lighthouse produces a parallel beam of light. The beacon consists of a bulb and a converging lens. Where should the bulb be placed?

nlens > noutside

F

  • At F
  • Inside F
  • Outside F

P.A. F

Physics 1161: Lecture 18, Slide 13

  1. Rays parallel to principal axis pass through focal point.
  2. Rays through center of lens are not refracted.
  3. Rays through F emerge parallel to principal axis.

Assumptions:

  • monochromatic light incident on a thin lens.
  • rays are all “near” the principal axis.

Converging Lens Principal Rays

F

F

Object

P.A.

Image is (in this case): Real or Imaginary Inverted or Upright Enlarged or Reduced

Physics 1161: Lecture 18, Slide 14

ACT: Converging Lens

Which way should you move object so image

is real and diminished?

(1) Closer to lens

(2) Further from lens

(3) Converging lens can’t create real

diminished image.

F

F Object

P.A.

Physics 1161: Lecture 18, Slide 15

Image Object

Object^ Image

Object

Image

3 Cases for Converging Lenses

This could be used as a projector. Small slide on big screen

This is a magnifying glass

This could be used in a camera. Big object on small film

Upright Enlarged Virtual

Inverted Enlarged Real

Inverted Reduced Real

Inside F

Past 2F

Between F & 2F