Thin Lens Equation

We started off Friday's class with Mr. Banow showing us how to derive the thin lens equation. Here is the link to the website: http://www.hirophysics.com/Anime/thinlenseq.html


The thin lens equation is:
1/di+1/do=1/f (which is exactly the same as the curved mirror equation)



M=hi/ho=-di/do

The sign rules are:
1. All distances are measured from the optical center
2. Distance of real images (behind the lens) are positive (virtual=negative)
3. Inverted=negative magnification, upright=positive

Examples:
1. A 8.0cm tall pencil is placed 17cm in front of a converging lens (with focal length of 10.0cm). How far and how tall will the image be?
ho=8.0cm
do=17cm
f=10.0cm
di=?
hi=?

1/di+1/do=1/f
1/di+1/17=1/10.0
1/di=1/10.0-1/17
di=24cm

hi/ho=-di/do
hi/8.0=-24/17
hi=-11cm

2. Where must a book be placed in front of a magnifying glass (converging, f=10.0cm), if a virtual image is to be formed 25cm in front of the lens? What is the magnification?
f=10.0cm
di=-25cm
do=?
M=?

1/di+1/do=1/f
1/-25+1/do=1/10.0
1/do=1/10.0-1/-25
do=7.1cm

M=-di/do
M=25/7.1
M=3.5x

http://www.youtube.com/watch?v=9pdEX4xtkLs

I don't know who is left to write the blog so whoever's last name comes first alphabetically of who is left can write it:)

Properties of Images

When the focal length is positive, the lens is converging. When the focal length is negative, the lens in diverging.

When stating the properties of an image there are generally four. Images are classified by their position, kind, attitude, and magnification.

Don't forget to draw your three lines when drawing a diagram!

Converging:

Distant: The image is behind the lens and at F. The image is real as well as inverted and smaller than the object.

Outside F`: The image is behind F and real. It is also the same size and flipped.

At F`: When there is an object at the focal length of a converging lens there is never an image.

Between F` and O: A virtual image that is in front of F will occur. The image is also larger then the object and upright.

Diverging:

Distant: The image is positioned in front of the lens at F. The image is also virtual as well as smaller than the original object. It remains upright when the light hits the lens.

Outside F, At F, Between F and O: The image is smaller, virtual, upright, and between F and O.

I pick.... jk i dont care who writes the next blog!

Converging and Diverging Lenses

At the beginnng of class we wrote a 10 question true and false quiz on the questions we inquired about that were presented and posted on the Wiki Page.

We then carried onto reviewing our sheets on what we learned in Tuesdays class; Contact Lenses, Eye Glasses, Artificial Lens, and Lasik Laser Eye Surgery.

As a class we inquired on several strange aspects of human eyes. We learned that when you die your pupils will in fact dilate because the muscles associated with your iris lose it's ability to control movement and becomes locked in a retracted state where the pupils appear to dilate. Then on Youtube we viewed a video of a man vibrating his eyes. Following that, we watched videos of a man who is capable of popping out his eyes by having strong control over his eye muscles.

We then took notes on Lenses - Converging and Diverging.

Lenses have curved surfaces or a very large number of flat surfaces located at slightly different angles

Converging/Convex Lense - (position lense) : thicker at the centre than at the edges

Diverging/Concave Lense - (negative lens) : thicker at the edges


After taking notes we analyzed a sheet of four different ray diagrams on converging and diverging lenses. By viewing these ray diagrams we were able to come up with three consistant rules that apply to every ray diagram:

1) The ray will go parallel and through F
2) The ray will go through F' and then parallel
3) The ray will go straight through O

Sorry I couldn't make it to class today Mr. Banow!! The next person to write a blog whoever who came latest to class... lol could be a few a options.

Correct Correction of Correct Correctness

...this title makes sense if you think about it.

In today's class, Mr. Banow set up four stations, each concerning a topic relating to eye correction:

• Contact Lenses
• Eye Glasses
• Artificial Lenses
• LASIK - Laser Eye Surgery

Contact Lenses

Contact Lenses are thin, transparent discs that sit on the cornea that can correct hyperopia (far-sightedness), myopia (near-sightedness), astigmatism, and presbyopia.

There are many different kinds of contact lenses, each with a different function. The six different types are daily-wear, extended-wear, disposable, colour-tinted, UV protection, and corneal reshaping.

Eye Glasses

Eye glasses are lenses that are attached to a frame. There are several different type of glasses:

• Corrective - changes the focal length in order to correct defects such as myopia or hyperopia

• Bifocal - allows for two different focal lengths so one can see near and far objects; the division is clearly visible

• Trifocal - similar to bifocal lenses, but with three different focal lengths

• Progressive - similar to bifocal, but the division is not visible as the lens is gradually changed

• Safety - used to protect the eye from physical damage

• Sunglasses - protects the eye from UV radiation

• Special - used for special functions, such as 3D red-cyan anaglyph glasses

Glasses are also made out of many different materials, such as crown glass, plastic, polycarbonate, Trivex, and high-index plastic. The material is chosen based on what the glasses are used for.

The lenses are either converging lenses (to treat myopia) or diverging lenses (to treat hyperopia).

The different types of lenses.

Artificial Lenses

Artificial lenses are replacement lenses for your eye. The two types are intraocular lens (IOL) and Crystalens. The Crystalens is considered to be superior because it can be manipulated by the ciliary muscles, but it costs more and requires a more intensive surgery.

LASIK - Laser Eye Surgery

LASIK is a medical surgery used to correct hyperopia, myopia, and astigmatism. A laser is pulsed on an exposed cornea, removing corneal tissue, therefore, reshaping it.

Procedure of LASIK:

1. Make an incision in the cornea to make a flap
2. Fold the flap back to expose the cornea
3. A laser is pulsed at the exposed cornea
4. The flap is replaced and any wrinkles or bubbles are smoothed

The surgery itself will only take a few minutes. The cornea will naturally seal back into place in a few hours and will completely heal in a matter of days.


At the end of class, we were instructed to watch a video from the Mythbusters Pirate Special. It can be found here if you have not already seen it.

The next blog will be written by whoever can figure out the title first!

Eye Projects

We started class by talking about our presentations and what we have to do, after that we moved on to Mr. Banow talking about how to make a wiki page. Following that we went to the computer lab for about 50 minutes to work on the projects.

And that is literally all we did that class, so not much to write about.. But there ya go :)

Vision, eyes.. and other stuff

In the begging of class we reviewed the last blog post (as usual)

and then started with a quiz that was based on the sheet we were given last class. (the human eye)

Next we also reviewed over our Animal vision booklets we had received the previous class.

Then we began all of the presentations on Eye Defects, where everyone was given a topic to research on eye defects and make a presentation about.

We learned a lot in the presentations:

Amblyopia (lazy eyes): the lack of

perfect vision.

usually blur vision in the effected eye. one eye or even both eyes wander to different spots and blur the vision. most patients don't notice the difference in vision but some people notice the eyes wondering to different

things in the room.

Treatments: patching the good eye or instilling tropical atropine in the eye for better vision.

Cataracts: A clouding that develops

in the lens of the eye. this can be caused by aging, ultra violet light, diseases (such as: diabetes) and others.

Treatments:

eye surgeries ECCE and ICCE

wearing sunglasses

and more

Myopia: near sightedness,

where the eyeball is longer that it normally should be which effects

the way light enters the eye.

can be caused hereditary.

Treatment:

corrective lenses

laser eye surgery

Colour Blindness:

inability to distinguish betweencertain colours, is

more common in men because it is effected by the X gene if it is damaged which would be more common in males. can be hereditary.

Treatments:

corrective lenses

contact lenses

Astigmatism:

when the cornea is abnormally curved and you cannot see properly. common in people who are near sighted.

Treatments:

corrective lenses

laser surgery

To end class Mr.B suggested another assignment involving presentations

Wiki Link

https://mrbanow.wikispaces.com/

Follow this to get to the Wiki for the Optics Applications assignment.