Transcript Converging and Diverging Lenses - SNC 2P - SNC 2P

Lenses

Lenses are transparent objects that are
used to refract light to help form an image

There are two types of lenses:
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DO NOT COPY
Converging lens
(aka Convex Lens)
Diverging lens
(aka Concave Lens)
Go experiment with shooting more than one
light ray through the different lenses in your
ray 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
O
2F’
F’
PA
F
2F
F = focal point
O = optical center
F’ = secondary focus
O
2F’ or 2F = focus length
from mirror x 2
2F
F
F’
PA
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 Mirror
Try 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
Cameras
BEFORE THE SHOT
Mirrors
AFTER THE SHOT
Viewfinder
Lenses
Shutter
Sensor
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
Lens #2



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 #1
Locating Images in Lenses
Do as activity
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