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Physics 7C SS1, Lecture 6: Ray Model

Lenses & Images

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Agenda Quiz 2 Review Ray model: lenses and images Introduce Field model:

Electric field and Force Analogies with gravitational field and force

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Quiz 2

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Lecture today should be…

a) Primarily about lenses

b) More lenses than fields

c) Even between lenses and fields

d) More fields than lenses

e) Primarily about fields

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Every part of the tree reflects light, scattering it all directions.

A ray diagram is used to simplify this picture.

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What type of image does Ernie make?

a) Realb) Virtualc) Uprightd) Invertede) Biggerf) Smaller

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c

Focal point, f

Obj

ect

plan

e

Imag

e pl

ane

o i

Imag

e pl

ane

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c

Focal point, f

Object plane

o

iImage plane

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Where will the image be?How big will the image be?

Thin-lens Equation

1 1 1

o id d f+ =

Magnification:

i

o

dm

d=−

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Terms in Optics Concepts:

Object Image

Real Virtual Upright Inverted

Magnification Focus

Ways to locate Image: Thin Lens Equation

Image distance Object distance Sign of lens

Ray Tracing Principal Rays

Lens Types: Converging Diverging Convex Concave

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c

Imag

e pl

ane

True/False: This is enough information to determine the focal point of the lens. If true, devise a procedure. If false, determine the minimal additional information necessary.

ImageObject

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You place a tiny source of light at the focal point

What happens?a) Rays all bend through the far focal point

b) Rays emerge parallel

c) Rays travel straight (looks like diverge from the near focal point)

d) Something else