Lenses
-
Upload
keith-warne -
Category
Education
-
view
10.824 -
download
0
description
Transcript of Lenses
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Lenses
K Warne
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Refraction of waves• Waves slow down
on entering a more dense medium.
• If the wave strikes this medium at an angle it then changes direction.
Normal line 90° to the surface
The wave bends towards the normal on entering a more dense medium at an angle.
The waves bend away from the normal when exiting a more dense medium.
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Refraction• Waves
bend towards the normal when entering a more dense medium.
Incident ray
Refracted ray
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Converging Lenses
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Diverging Lenses
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Ray Diagrams - Optical Centre
Principle axis
In a thin lens the displacement is negligible. The rays are drawn as if refracting from the center line.
.F
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Ray Diagrams - Optical Centre
Principle axis
Light rays passing along the principle axis are not refracted as they strike both surfaces at 90°
Any ray passing through the Optical centre can be thought of as passing straight through.
In a thin lens the displacement is negligible.
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Ray Diagrams -Focal Point
…………………….
… ....
F ……... ………..
•
Any ray striking the lens ………… to the principle axis is refracted through the …………….. point.
These values are the ………… for either side of a ………...………… lens.
Parallel to ………………… ………..
…………….…….
•••
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Diverging Lenses
F
F -……. ……….
……. …………..•
In a diverging lens the rays …………………. to have originated at the ……………… point.
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Convex lens Images
Object on one side an image is formed on the ……….. side. Image properties:
• ………… (can be cast on a ………..) (type)
• ...................................………… (position)
• ……….. than the object (…………………) (size)
• and ……………………... (orientation)
Object
………….
…… …….
…..
…2F F F 2F••• ••
Magnification or Di
screen
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Diverging Lenses
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Light PracticalGroup 1 - Part I
Measure the angle of incidence when the angle of refraction is 90°
Part II GROUP 2-5 - Part 2
• Optical bench - measure the distance from the object to the lens, height of the object and the distance from the image to the lens and the height of the image.
Do Ho Di Hi
1
2
3
4
GROUP 6 & 7 Diagrams (Ray Diagrams)
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Convex lenses Do=2F
Object placed at 2F the image is:
• Real
• At 2F
• Same size as object
• inverted
Ho
Object
Image
Do Di
HiF= 50cm
2F F F 2F
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Ray Diagrams -Object closer than the Focal length
Image -
• ………………………
• ……………………
• ……………………..
• ………………………..
F F••
An object placed between F and the lens.
The lens would now be functioning as a ……………………………..
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Light Practical
Object Image
Do Di
Ho Hi
Do greater than 2F
Do equal to 2F
Do less than 2F
F= 50cm
Ray diagrams p 39
2F
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
From World Book © 2002 World Book, Inc., 233 N. Michigan Avenue, Suite 2000, Chicago, IL 60601. All rights reserved. World Book illustrations by Charles Wellek
From World Book © 2002 World Book, Inc., 233 N. Michigan Avenue, Suite 2000, Chicago, IL 60601. All rights reserved. Nikon, Inc.
Eye vs CameraEye vs CameraPupilIrisRetinaLens
Discuss the nature of the image formed in terms of size, position, orientation and type.
Also discuss how focusing and controlling the amount of light entering is achieved in both.
LensAppetureFilm
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Eye - DefectsEye - Defects
This is commonly called short sighted.
Distant object brought ‘closer’
Distant objects the lens is not stretched enough. (Too fat)
Rays are focused in front of retina.
Object close up are focused clearly.
A diverging lens would cause distant rays to focus on the retina and normal sight is restored.
Short Sighted
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Compound Microscope
F•
2F
F F 2F
View this slide as slide show!
SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYFor For FULLFULL presentation click presentation click HERE >> ScienceCafeHERE >> ScienceCafe
Hi -
This is a SAMPLE presentation only.
My FULL presentations, which contain loads more slides and other resources, are freely available on my resource sharing website:
www.sciencecafe.org.za
(paste into your browser if link above does not work)Have a look and enjoy!
Keith Warne