Lenses Lenses are transparent objects that are used to refract light to help form an image There are two types of lenses: 1.

Lenses Lenses are transparent objects that are

used to refract light to help form an image

There are two types of lenses:

1

Converging lens (aka

Convex Lens)

Diverging lens (aka Concave

Lens)

DO NOT COPY

Go experiment with shooting more than onelight ray through the different lenses in yourray box kits

what does a converging lens do to light?

What does a diverging lens do to light?

What happens when you shine light through one lens, and then the other?

Which lens is like the one in your eye? Glasses?

Find the F and mark. What happens when you shoot a ray through the F? Shoot a ray parallel to PA? Shoot a ray through O?

1. Converging lens (aka Convex Lens)

Thicker in the center than at edges

causes parallel light rays to converge (come together) to a single focus point after refraction.

2. Diverging lens (aka Concave Lens)

Thicker in the edges than at center

causes parallel light rays to diverge (spread out) after refraction.

Lens Terminology

PA = principle axis

F = focal point

O = optical center

F’ = secondary focus

2F’ or 2F = focus length

from mirror x 2 PAF

O

F’2F 2F’

PAF’

O

F2F’ 2F

Light Ray Rules

1. A ray shone parallel to axis is refracted through the F.

2. A ray shone through F’ is refracted parallel to PA.

3. A ray shone through O does not refract and goes straight through

Locating Images in Converging Lenses:

Case 1: An object outside 2F’

Case 2: An object between 2F’ and F’

Case 3: An object on F’

Case 4: An object between F’ and MirrorTry Worksheet –

Converging lenses ONLY

Applications of Converging Lenses:

1. Magnifying Glass

- image is enlarged

- object must be between focal length and lens

2. Camera’s

- the mirror goes up and stops reflecting image to the viewfinder.

- The shutter opens and the film or sensor is exposed to form inverted image

AFTER THE SHOT

LensesMirrors

Sensor

Viewfinder

Shutter

BEFORE THE SHOT

Cameras

When the person is ready to take the photo, the mirror goes up and stops reflecting image to the viewfinder.

The shutter opens and the film or sensor is exposed – information is collected to create the negative or digital image.

3. Eyes- lens focus and inverts image to back of eye (retina)- Your brain is what really flips the image.

4. Glasses - far sighted = can’t

see near because eye converges beyond retina.

- Converging lens refocuses light onto retina

The sheep eye has 4 external attached muscles which control the eye movement. The human eye has six. The additional muscles allow humans the ability to “roll” and move their eyes in all directions.

Although the muscles of each eye work collectively as a team, the eyes themselves do not focus or work together until months after birth. Most people have one dominant eye.

Which eye is your dominant eye?

5. Movie Projector

- film has images inverted so they appear upright on screen

Telescopes

Uses two converging lens to project an upright, real image into eye.

The first converging lens, projects image, but it is inverted.

The second converging lens takes image and projects it as upright into the users eye.

Lens #2 Lens #1

Locating Images in Lenses

Do as activity

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