Uses of Mirrors & Lenses What are some commercial uses of lenses? What are some commercial uses...

Open to 5.2

Can you see the buck?(not the doe)

Uses of Mirrors & Lenses

What are some commercial uses of lenses? Glasses/ Contacts Projectors Cameras Microscopes Telescopes Binoculars*

Camera

Telescope

Clip

Binoculars

Projector

Microscope

Clip

Mirrors & Lenses

Convex

Concave

Mirascope

Converging – light rays come together

Diverging – light rays spread out

Mirrors & Lenses

Types of Images

Virtual Image right-side-up cannot be projected on a screen

Real Image upside-down can be displayed on a screen*

Image formation

Distance affects the angle of view

Far away- small angle of view allows very little detail to be seen

Closer- larger angle of view creates more details to be seen

Ray Diagram Setup

Principal axis- line in a lens that joins the centers of curvature of the lens surface

Ray Diagram Setup

Focal point- point at which a beam of parallel light, to the principal axis, converges

Ray Diagram Setup

Focal Plane- all possible points on a plane for the location of the focal point

Ray Diagram Setup

Focal length- distance between center of lens and its focal point

Ray Diagrams:

Copy the instructions on the next few slides and then we will look at the rules in a virtual “draw”.

How to draw a mirror ray diagram:

1. parallel to the axis then go through the focal point.

2. to the center of the mirror then out at the same angle.*

Let’s draw a correct ray diagram

The scope of vision looks like this in yellow.

The first blue ray goes from the top of the object – parallel to the “principal axis” and comes back at the same angle (90)

Let’s draw a correct ray diagram

There is no focal point on a flat mirror.

If we are wanting to begin at the top of the ‘P’ - the angle is whatever you choose with the red arrow

http://www.regentsprep.org/Regents/physics/phys09/bcraytrace/default.htm

How to draw a lens ray diagram:

1. parallel to the axis then to through the focal point.

2. straight through the center of lens. *

http://www.regentsprep.org/Regents/physics/phys09/bcraytrace/default.htm

Let’s draw a correct ray diagram

Let’s draw a correct ray diagram

More practice

More practice

Mirror & Lens Equation

Focal length

io ddf

111

distance to imagedistance

to object

do = 15.5 cm

f = 15.0 cm di = ?

io ddf

111

id

1

5.15

1

15

1

15.5

1

15

1

d

1

i

cm 654d i

Example) Mr. Nelson is showing slides to his physics class, if the slides are positioned 15.5 cm from the projector lens that has a focal length of 15.0 cm, where should the screen be placed to produce the clearest image of the slide?

Power of Eyeglasses

fP

1

Power – measured in diopters (1/meter)

focal length (m)*

P = ?f = .30 m

fP

1

30.0

1P

diopters 33.3P

Example) Beth is farsighted, so she must wear glasses to see objects close by. If her glasses have a focal length of 0.30 m, what is their power in diopters?

Image Size Magnification- image is observed

through a wider angle with the use of a lens

o

i

h

hM

Magnification

object height*

image height*

Practice Problem

As you look through your binoculars at a deer out in the field, the deer appears to be 3 m tall but the deer in real life is only 1 m tall. How much magnification do your binoculars have?

As you look through your binoculars at a deer out in the field, the deer appears to be 3 m tall but the deer in real life is only 1 m tall. How much magnification do your binoculars have?

o

i

h

hM

m

mM

1

3 xM 3

Mirror and Lens Overview

Lemony Snickets Clip

Talking on a LASER Demo

http://www.andrews.edu/phys/wiki/PhysLab/doku.php?id=lab10

lab