I.I. What is Visible lightWhat is Visible lightA. EM radiation that has A. EM radiation that has

a wavelength rangea wavelength rangeof about 750-380 nmof about 750-380 nm

B. Includes ROY G BIVB. Includes ROY G BIV1.1. Red-Wavelength of 750-620Red-Wavelength of 750-620

2.2. Orange-Wavelength of 620-590Orange-Wavelength of 620-590

3.3. Yellow-Wavelength of 590-570Yellow-Wavelength of 590-570

4.4. Green-Wavelength of 570-495Green-Wavelength of 570-495

5.5. Blue-Wavelength of495-450Blue-Wavelength of495-450

6.6. Indigo-Wavelength of 450-420Indigo-Wavelength of 450-420

7.7. Violet-Wavelength of 420-380Violet-Wavelength of 420-380

C. As wavelength changes the color changes-C. As wavelength changes the color changes-

C. Travels at 300,000Km/sec no matter C. Travels at 300,000Km/sec no matter what color or intensity of the light – what color or intensity of the light – TRAVELS AT THE SAME SPEED!!!!TRAVELS AT THE SAME SPEED!!!!

D. Intensity is determined by the D. Intensity is determined by the amplitude of the light wave amplitude of the light wave

E. Energy increases as the frequency E. Energy increases as the frequency increasesincreases

-What Color of light is highest in -What Color of light is highest in energy?energy?

ExamplesExamples-Wood -Metal-Cotton-Wool-Wood -Metal-Cotton-Wool

II. How we see!II. How we see!

A. When light strikes an object the light A. When light strikes an object the light can be reflected, absorbed or can be reflected, absorbed or transmittedtransmitted

Most objects reflect or absorb lightMost objects reflect or absorb light

1.Objects we can’t see 1.Objects we can’t see through are called through are called

opaqueopaque..

a. They reflect or absorb a. They reflect or absorb all all the light that hits them! the light that hits them! You You cannot see through themcannot see through them

Examples:Examples:-Clear Glass-Clear Glass-Water-Water-Air-Air

2. Objects we can 2. Objects we can see through are see through are TransparentTransparent

a.They allow a.They allow light to be light to be

transmitted transmitted through them through them allowing you to allowing you to see what is on see what is on the the other sideother side

ExamplesExamples-Frosted -Frosted GlassGlass-Wax Paper-Wax Paper

3. Objects that we see 3. Objects that we see as milky or allow as milky or allow some light to come some light to come through are called through are called translucenttranslucent..

a. They allow a. They allow some some light through light through but but reflect reflect (scatter) (scatter) some some as wellas well

B. Types of MirrorsB. Types of Mirrors

1. Plane (flat) Mirrors produce an image 1. Plane (flat) Mirrors produce an image that is right side up and the same size as that is right side up and the same size as the object being reflectedthe object being reflected

a. Plane mirrors produce “virtual a. Plane mirrors produce “virtual images” which are right-side up or images” which are right-side up or upright upright (you can see it but it doesn’t (you can see it but it doesn’t actually actually exist – you can’t reach behind exist – you can’t reach behind a mirror a mirror and touch your image)and touch your image)

2. Concave Mirrors 2. Concave Mirrors curve inward like a curve inward like a bowl and can form bowl and can form virtual or real virtual or real imagesimages

a. real images a. real images are formed when are formed when rays actually rays actually meet a point, meet a point, they are inverted they are inverted or upside downor upside down

A,B If the object is farther from the mirror A,B If the object is farther from the mirror than the focal point the image is realthan the focal point the image is realC If the object is between the mirror and C If the object is between the mirror and focal point the image is virtualfocal point the image is virtualWhat is a real and virtual image?What is a real and virtual image?

3. Convex mirrors have a surface 3. Convex mirrors have a surface that curves outward and since the that curves outward and since the rays don’t actually ever meet, the rays don’t actually ever meet, the images formed are always virtualimages formed are always virtual

a. “objects seen in the mirror are a. “objects seen in the mirror are closer than they appear” - Explaincloser than they appear” - Explain

b. Because convex mirrors spread out b. Because convex mirrors spread out rays of light you see a larger reflection rays of light you see a larger reflection area so because you see more the area so because you see more the images appear smaller and father away images appear smaller and father away than they actually arethan they actually are

example – Rainbowexample – RainbowWater dropletsWater droplets

III Refraction and III Refraction and LensesLenses

A. Refaction is A. Refaction is when light rays when light rays enter a new enter a new medium at an medium at an angle, the angle, the change in speed change in speed causes them to causes them to bend or change bend or change directiondirection

Some mediums cause light to bend more Some mediums cause light to bend more than others. As light passes from a less than others. As light passes from a less dense medium into a more dense medium, dense medium into a more dense medium, it slows and is refracted – below is an index it slows and is refracted – below is an index of refraction for different mediumsof refraction for different mediums

1. It can also cause you to see 1. It can also cause you to see something that is not actually something that is not actually therethere

Example Mirage –What causes a Mirage?Example Mirage –What causes a Mirage?

2.2. Raindrops act like tiny prisms, Raindrops act like tiny prisms, refracting and reflecting the light refracting and reflecting the light and separating the colors – Violet and separating the colors – Violet (shortest) is refracted the most and (shortest) is refracted the most and Red (longest) is refracted the leastRed (longest) is refracted the least

B. A lens is a curved piece of glass or B. A lens is a curved piece of glass or other transparent material used to other transparent material used to refract lightrefract light

1. A lens forms an image by 1. A lens forms an image by refracting light rays that pass refracting light rays that pass through it – like mirrors, lenses can through it – like mirrors, lenses can have different shapeshave different shapes

C. A concave lens is C. A concave lens is thinner in the thinner in the center than at the center than at the edges. As parallel edges. As parallel light passes light passes through they are through they are bent away from the bent away from the center spreading center spreading out and appear to out and appear to come from the focal come from the focal point (produces point (produces virtual images)virtual images)

D. A convex lens is D. A convex lens is thicker in the thicker in the center than at center than at the edges. As the edges. As parallel light parallel light passes through it passes through it is bent towards is bent towards the center and the center and meet at the focal meet at the focal point – the more point – the more curved the more curved the more it refractsit refracts

IV. Seeing LightIV. Seeing Light

A. Cornea A. Cornea 1.Light Enters through this 1.Light Enters through this transparent front surfacetransparent front surface2. Protects the eye2. Protects the eye3. Acts as a lens bending light3. Acts as a lens bending light4. Each time you blink your eye 4. Each time you blink your eye lids act like windshield wipers lids act like windshield wipers cleansing and moistening cleansing and moistening

B. IrisB. Iris

1. Ring of muscle that contracts 1. Ring of muscle that contracts and expands chaning the amount and expands chaning the amount of light entering the eyeof light entering the eye

2. Gives the eye its color2. Gives the eye its color

3. Most brown, can be blue or 3. Most brown, can be blue or greengreen

C. PupilC. Pupil

1. Looks black, actually a hole 1. Looks black, actually a hole covered by the clear corneacovered by the clear cornea

2. Opening into the dark inside of eye2. Opening into the dark inside of eye

3. Size depends on contraction of iris3. Size depends on contraction of iris

4. Dim light it gets larger (allows more 4. Dim light it gets larger (allows more light in), bright light it gets smaller light in), bright light it gets smaller (reducing the light that enters)(reducing the light that enters)

D. LensD. Lens

1. Behind the pupil is a convex lens1. Behind the pupil is a convex lens

2. Refracts light forming an image on 2. Refracts light forming an image on the lining of your eyeballthe lining of your eyeball

3. Cilliary muscles cause lens to 3. Cilliary muscles cause lens to change shape when you focuschange shape when you focus

a. Focusing on distant a. Focusing on distant objects causes the ciliary objects causes the ciliary muscles to relax making muscles to relax making the lens longer and the lens longer and

thinnerthinnerb. Focusing on nearby b. Focusing on nearby objects the muscles objects the muscles

contract and the lens contract and the lens becomes shorter and becomes shorter and fatterfatter

E. Layer of cells lining the inside of the E. Layer of cells lining the inside of the eyeball is the retinaeyeball is the retina

1. As the cornea and lens refract 1. As the cornea and lens refract light, an upside down image is light, an upside down image is formed on the retinaformed on the retina

2. Retina is made up of millions of 2. Retina is made up of millions of tiny light sensitive cells called rods tiny light sensitive cells called rods and conesand cones

a. Rods respond to small a. Rods respond to small amounts amounts of light (important in of light (important in night vision) night vision) b. allow to distinguish b. allow to distinguish between between black, white and greyblack, white and grey

b. Cones respond to colors. b. Cones respond to colors. Cone cells function in bright Cone cells function in bright light that is why it is difficult to light that is why it is difficult to distinguish between colors in distinguish between colors in dim lightdim light

– Three types of cones:Three types of cones:1.1.Red lightRed light2.2.Green lightGreen light3.3.Blue lightBlue light

F. The signals generated by the rods F. The signals generated by the rods and cones are sent to the brain via and cones are sent to the brain via the optic nerve.the optic nerve.

1. When signals reach your brain 1. When signals reach your brain they are automatically turned right they are automatically turned right side upside up

2. The two images from each eye are 2. The two images from each eye are combined into a single 3-D imagecombined into a single 3-D image

Stare at the bottom right star of the Stare at the bottom right star of the flag for at least 60 seconds. Do not flag for at least 60 seconds. Do not move or blink your eyes during that move or blink your eyes during that time. Then stare at a blank white time. Then stare at a blank white sheet of papersheet of paper

Why do you see red, white and blue?Why do you see red, white and blue?

Complimentary colors Complimentary colors

Now try staring at the red, white and Now try staring at the red, white and blue flag and then look at the white blue flag and then look at the white paper.paper.

G. A nearsighted person can see nearby things G. A nearsighted person can see nearby things clearly, but objects at a distance appear blurry. clearly, but objects at a distance appear blurry.

1. This happens because the eyeball is 1. This happens because the eyeball is a a little to longlittle to long2. This is fixed by wearing glasses with 2. This is fixed by wearing glasses with a a concave lens, spreading the rays concave lens, spreading the rays farther farther before they enter the eyebefore they enter the eye

H. A farsighted person can see distant H. A farsighted person can see distant objects clearly but close objects are blurry.objects clearly but close objects are blurry.

1. This happens because the eyeball is too 1. This happens because the eyeball is too shortshort

2. Fixed by wearing glasses with a convex 2. Fixed by wearing glasses with a convex lens - makes the rays bend towards each lens - makes the rays bend towards each other a little before they enter the eye.other a little before they enter the eye.