VISION AND OPTICAL INSTRUMENTS

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Preliminaries• The Human Eye • Vision Defects • Optical Instruments

– Camera– Telescope– Microscope

• Colors

THE HUMAN EYE

If the our eye has a lens, how is it possible for us to visualize things set at different distances? Is this a violation of the lens equation?

Accommodation• The ability of our lens to

change shape or its focal length to see an image in detail if the object is set at different distances.

• The lens of the human eye is controlled by a set of ciliary muscles.

VISION DEFECTS

Vision Defects • When the eye loses its ability

to change its shape of its lens, vision becomes poor and defective.

Nearsightedness or Myopia• This happens when a person

can see near objects clearly but has difficulty focusing on far objects.

• This occurs when the eye has a LONG eyeball and the lenses are too CONVEX

Myopia can be corrected by wearing a concave lens.

Farsightedness or Hyperopia• This happens when a person

can see very far objects clearly but has difficulty focusing on near objects.

• Eyeball is too short and the lens is too flat that causes the image to be formed behind the retina.

Hyperopia can be corrected by wearing a convex lens.

Presbyopia• As a person grows older,

vision becomes poorer. • Decrease in the elasticity of

the lens and lessened ability of the eye muscle to increase the roundness of the lens

Presbyopia can be corrected by wearing bifocals.

Astigmatism• This occurs when there is

unevenness in the curvature of the lens of the eyeball.

Astigmatism can be corrected by wearing cylindrical lenses.

Cataracts• These occur when the lens of

the eye becomes opaque due to overexposure to radiation, drug use, smoking, medications and heredity.

• Can be removed surgically

How are you going to take care of your eyes?

OPTICAL INSTRUMENTS

The human eye has a limited range of vision.

We need extensions to make our range of vision wider.

Reflecting Telescope

Refracting Telescope

COLORS AND VISION

Color Addition

Color Subtraction