Presentation on theme: "I.What is Visible light A. EM radiation that has a wavelength range of about 750-380 nm."— Presentation transcript:
I.What is Visible light A. EM radiation that has a wavelength range of about 750-380 nm
B. Includes ROY G BIV 1.Red-Wavelength of 750-620 2.Orange-Wavelength of 620-590 3.Yellow-Wavelength of 590-570 4.Green-Wavelength of 570-495 5.Blue-Wavelength of495-450 6.Indigo-Wavelength of 450-420 7.Violet-Wavelength of 420-380 C. As wavelength changes the color changes-
C. Travels at 300,000Km/sec no matter what color or intensity of the light – TRAVELS AT THE SAME SPEED!!!! D. Intensity is determined by the amplitude of the light wave E. Energy increases as the frequency increases -What Color of light is highest in energy?
Examples -Wood -Metal-Cotton-Wool II. How we see! A. When light strikes an object the light can be reflected, absorbed or transmitted Most objects reflect or absorb light 1.Objects we can’t see through are called opaque. a. They reflect or absorb all the light that hits them! You cannot see through them
Examples: -Clear Glass -Water -Air 2. Objects we can see through are Transparent a.They allow light to be transmitted through them allowing you to see what is on the other side
Examples -Frosted Glass -Wax Paper 3. Objects that we see as milky or allow some light to come through are called translucent. a. They allow some light through but reflect (scatter) some as well
B. Types of Mirrors 1. Plane (flat) Mirrors produce an image that is right side up and the same size as the object being reflected a. Plane mirrors produce “virtual images” which are right-side up or upright (you can see it but it doesn’t actually exist – you can’t reach behind a mirror and touch your image)
2. Concave Mirrors curve inward like a bowl and can form virtual or real images a. real images are formed when rays actually meet a point, they are inverted or upside down
A,B If the object is farther from the mirror than the focal point the image is real C If the object is between the mirror and focal point the image is virtual What is a real and virtual image?
3. Convex mirrors have a surface that curves outward and since the rays don’t actually ever meet, the images formed are always virtual a. “objects seen in the mirror are closer than they appear” - Explain
b. Because convex mirrors spread out rays of light you see a larger reflection area so because you see more the images appear smaller and father away than they actually are
example – Rainbow Water droplets III Refraction and Lenses A. Refaction is when light rays enter a new medium at an angle, the change in speed causes them to bend or change direction
Some mediums cause light to bend more than others. As light passes from a less dense medium into a more dense medium, it slows and is refracted – below is an index of refraction for different mediums
1. It can also cause you to see something that is not actually there Example Mirage –What causes a Mirage?
2. Raindrops act like tiny prisms, refracting and reflecting the light and separating the colors – Violet (shortest) is refracted the most and Red (longest) is refracted the least
B. A lens is a curved piece of glass or other transparent material used to refract light 1. A lens forms an image by refracting light rays that pass through it – like mirrors, lenses can have different shapes
C. A concave lens is thinner in the center than at the edges. As parallel light passes through they are bent away from the center spreading out and appear to come from the focal point (produces virtual images)
D. A convex lens is thicker in the center than at the edges. As parallel light passes through it is bent towards the center and meet at the focal point – the more curved the more it refracts
A. Cornea 1.Light Enters through this transparent front surface 2. Protects the eye 3. Acts as a lens bending light 4. Each time you blink your eye lids act like windshield wipers cleansing and moistening
B. Iris 1. Ring of muscle that contracts and expands chaning the amount of light entering the eye 2. Gives the eye its color 3. Most brown, can be blue or green
C. Pupil C. Pupil 1. Looks black, actually a hole covered by the clear cornea 2. Opening into the dark inside of eye 3. Size depends on contraction of iris 4. Dim light it gets larger (allows more light in), bright light it gets smaller (reducing the light that enters)
D. Lens 1. Behind the pupil is a convex lens 2. Refracts light forming an image on the lining of your eyeball 3. Cilliary muscles cause lens to change shape when you focus
a. Focusing on distant objects causes the ciliary muscles to relax making the lens longer and thinner b. Focusing on nearby objects the muscles contract and the lens becomes shorter and fatter
E. Layer of cells lining the inside of the eyeball is the retina 1. As the cornea and lens refract light, an upside down image is formed on the retina 2. Retina is made up of millions of tiny light sensitive cells called rods and cones a. Rods respond to small amounts of light (important in night vision) b. allow to distinguish between black, white and grey
b. Cones respond to colors. Cone cells function in bright light that is why it is difficult to distinguish between colors in dim light –Three types of cones: 1.Red light 2.Green light 3.Blue light
F. The signals generated by the rods and cones are sent to the brain via the optic nerve. 1. When signals reach your brain they are automatically turned right side up 2. The two images from each eye are combined into a single 3-D image
Stare at the bottom right star of the flag for at least 60 seconds. Do not move or blink your eyes during that time. Then stare at a blank white sheet of paper
Why do you see red, white and blue? Complimentary colors Now try staring at the red, white and blue flag and then look at the white paper.
G. A nearsighted person can see nearby things clearly, but objects at a distance appear blurry. 1. This happens because the eyeball is a little to long 2. This is fixed by wearing glasses with a concave lens, spreading the rays farther before they enter the eye
H. A farsighted person can see distant objects clearly but close objects are blurry. 1. This happens because the eyeball is too short 2. Fixed by wearing glasses with a convex lens - makes the rays bend towards each other a little before they enter the eye.