Light 3-3Light 3-3IlluminatedIlluminated- object that can be seen - object that can be seen because it reflects light because it reflects light

Luminous- Luminous- object that gives off its own lightobject that gives off its own light

Common types of lights:Common types of lights:

IncandescentIncandescent

FluorescentFluorescent

NeonNeon

Sodium vaporSodium vapor

Tungsten-halogenTungsten-halogen

Light 3-3Light 3-3 Incandescent lights-Incandescent lights- glows when a tungsten glows when a tungsten

filament gets “white hot” filament gets “white hot”

not efficient 10% visible not efficient 10% visible light and 90% infrared light and 90% infrared (why a bulb gets hot) (why a bulb gets hot)

Fluorescent lightsFluorescent lights – glass tube that contains – glass tube that contains gas and powder. When electrical current gas and powder. When electrical current goes through the tube the gases give off goes through the tube the gases give off ultraviolet waves that hit the powder which ultraviolet waves that hit the powder which produces visible lightsproduces visible lights

Light 3-3Light 3-3 Neon lights –Neon lights – different gases are placed in a different gases are placed in a

sealed tube, electricity is sent through the sealed tube, electricity is sent through the tube, the gases absorb the energy for a tube, the gases absorb the energy for a short short time. Give off the energy as different time. Give off the energy as different colored light.colored light.

Sodium Vapor lights – Sodium Vapor lights – solid sodium, neon and solid sodium, neon and argon gas a placed in the light, the gases argon gas a placed in the light, the gases are heated by electricity, sodium changes are heated by electricity, sodium changes from solid to gas, sodium begins to give off from solid to gas, sodium begins to give off yellow lightyellow light

Light 3-3Light 3-3 Tungsten-halogen lights- Tungsten-halogen lights- contain tungsten contain tungsten

filament and a halogen gas, electricity filament and a halogen gas, electricity makes makes the filament glow, halogen gas the filament glow, halogen gas makes the makes the filament give off bright white light.filament give off bright white light.

Bioluminescence –Bioluminescence – chemical reaction between chemical reaction between proteins and oxygen in an proteins and oxygen in an organism. Almost all light organism. Almost all light not heat not heat

Light 3-4Light 3-4 Parts of the eye:Parts of the eye: Cornea-Cornea- transparent lens on the front of the eye transparent lens on the front of the eye

bends light rays, protects against bends light rays, protects against dust, dust, cleaned and moistened by the cleaned and moistened by the eyelideyelid

Iris-Iris- “colored” part of eye, ring of muscle that “colored” part of eye, ring of muscle that contracts or expands to change the contracts or expands to change the amount of light that enters the eyeamount of light that enters the eye

PupilPupil- looks black is actually a hole covered by - looks black is actually a hole covered by cornea. In dim light the iris expands exposing cornea. In dim light the iris expands exposing more of pupil (letting more light in) In bright light more of pupil (letting more light in) In bright light the iris contracts making the pupil smaller the iris contracts making the pupil smaller (letting less light in)(letting less light in)

Light 3-4Light 3-4 Lens Lens – convex lens that refracts an image on – convex lens that refracts an image on

the lining of your eyeball. Muscles contract the lining of your eyeball. Muscles contract or expand to change the lens depend on or expand to change the lens depend on how close or far away the object is.how close or far away the object is.

Retina- Retina- made of millions of cells called rods and made of millions of cells called rods and cones, an upside down image of cones, an upside down image of

what what you see is refracted on to the you see is refracted on to the retina.retina.

RodRod- detect white, black, and gray help you see - detect white, black, and gray help you see dim light and night vision dim light and night vision

ConeCone – respond to color cones for red, green, and – respond to color cones for red, green, and blue only work in bright light blue only work in bright light

Light 3-4Light 3-4 Optic nerve –Optic nerve – thick nerve that sends the signal thick nerve that sends the signal

to the brain to the brain

brain combines the two images into one 3-D brain combines the two images into one 3-D image and flips the image right side up.image and flips the image right side up.

NearsightedNearsighted -can see objects that are near, -can see objects that are near, difficulty with far way objects. difficulty with far way objects. eyeball is too long, corrected with eyeball is too long, corrected with

concave lenses concave lenses

Farsighted-Farsighted- can see objects that are far, difficulty can see objects that are far, difficulty with near objects, corrected with a with near objects, corrected with a convex lenses convex lenses