10Demo:

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Warm-Up Exercise1. A mirror reflects an object at a distance of

10 cm with an image that is 18 cm away. 1. Where is the focus?2. What is the radius of the circle?

2. An object is 20 cm tall and is magnified to 57 cm tall. What is the magnification?

3. Solve the following:1. 4x105 + 2.3x10-3

4. BONUS :Is there something “more” to this scene?

Optics• Tomorrow:

▫ QUIZ, Ray Diagrams Drawing and labeling Ray

diagrams Refraction Concepts of mirrors, SALT Magnification and focal lengths

• LESSON:▫ The Eye▫ Eye tests

• Classwork

•An ophthalmologist is a physician who specializes in eye care

Dominant Eye Test1. Extend both hands forward of your body and

place the hands together making a small triangle (approximately 1/2 to 3/4 inch per side) between your thumbs and the first knuckle.

2. With both eyes open, look through the triangle and center something such as a doorknob or the bullseye of a target in the triangle.

3. Close your left eye. If the object remains in view, you are right eye dominant. If your hands appear to move off the object and move to the left, then you are left eye dominant.

The Amsler Grid(Tests for age-related macular degeneration – AMD)1.Stand 12 inches to 14 inches

away (generally a comfortable reading distance).

2.If you wear glasses, keep them on.

3.Cover one eye and look at the dot in the center of the grid.

4.Watch for:1. Distortions or breaks in the lines of the grid. 2. Disappearing of lines3. Blurring or grey areas 4. Distortion or wavy lines 5. Holes or spots in any areas of the grid

The Snellen Chart •An eye chart used to

measure visual acuity•Named after the Dutch

ophthalmologist Herman Snellen (1862)

•Uses combinations of 10 letters

• (Ensure the top letter is 88.7 mm tall)• Viewers read from 20 feet away

Reading a Snellen Chart 20/20• Standard acuity.

20/40• You can read at 40 feet

what someone can read at 20 feet etc.

20/200• Inability to read the top

letter from 20 feet is considered “legally blind”

The Human Eye

Cornea1. The outer surface of your eye 2. Transparent layer of tissue3. Contributes 65-75% of the eye’s total

focusing power

Pupil

•a hole that allows light to pass through the eye

•Enlarges in the dark or when stimulated

Iris•It is created by the circular band of muscle.

•Determines your eye color

•The iris controls the size of the pupil

Retina•It is the inner lining in the back of the eye and is a projection screen for the light entering your eye

Detecting Light

Photoreceptors

• Enable you to see. This is how the light rays are absorbed.

Rod Cells

• Help us detect shape and movement in the dark.

Cone Cells

• Detect colour

Do Eyes Change Shape?•What type of lens is in front of your eye?

•This convex lens is attached to a tiny circle of muscles that can adjust its shape

•Why do aged people lose their vision?

Laser Eye Surgery•Two main types of

corrective eye surgery:

PRK

• Uses a precise laser to reshape the cornea

LASIK

• Cuts the cornea and inserts a corrective lens under the flap

Finding your Blind Spot

1. Your face should be very close to the screen.

2. Cover right eye and focus the left eye on the X.

3. Now slowly move away /toward from the screen.

4. The O will disappear, while the A which is further to the left is still visible.

As you move further away, the O will reappear. (Observe that you do not see a hole. Instead of the O you see a uniform grey background.

The "hole" is filled in by your brain. Make sure there is not a glare on the screen as it will obscure the whole vision.)

A O X

Blind spot

• Place where the optic nerve attaches to the retina

Optic nerve

• connects your eye to the brain

Vision ProblemsFar-sighted

• can see distant objects but not things close to them

Near-sighted

• can see objects close to them but not far away

Astigmatism• eye is unable to see a sharp image• irregular shape of cornea

Color Blind TestWhat do you see?

Color Blind TestWhat do you see?

Color Blind TestWhat do you see?

Color Blind TestWhat do you see?

Color Blind TestYou should see one or more pictures at the right

Color Blind TestYou should see one or more pictures at the right

Color Blind TestWhat do you see?

Color Blind TestWhat do you see?

Colour and Vision•Most people who are legally blind are able to see some light

•Colour blindness ▫The ability to only see shades of grey.

▫It occurs in 1 in 40,000 people.▫The ability to see some colour but not others.

Review

Class Work•Pg. 481 #1,5,7,8,12,14