1. Color & Polarization and Refraction
Hannah Huether
Mrs. Grayot, Physics, 6th
Wave Project
Color & Polarization and Refraction

2. Color
Objects absorb certain wavelengths from the light that strikes them and reflects the rest of the light.
The object’s color depends on which wavelengths are absorbed and which are reflected
If an object reflects all incoming light it looks the color of the light

3. Characteristics
Objects with a specific color will absorb all wavelengths EXCEPT that color
Objects that don’t reflect light look black
Chlorophyll- primary pigment that gives leaves a green color
In the fall, this pigment is destroyed allowing other colors to be reflected by the leaves

4. Primary Colors

5. Additive vs Subtractive
Combination of subtractive primary colors
Combination of additive primary colors

6. Polarization
Linear Polarization- the alignment of electromagnetic waves in such a way that the vibrations of the electric fields in each of the waves are parallel to each other.
In an electromagnetic wave, the electric field is at right angles to both the magnetic field and the direction of propagation.

7. Unpolarized Light
Typical sources produce light that consists of waves that have electric fields oscillating in random directions
This light is considered unpolarized
Light can be linearly polarized through transmission
Unpolarized light can become linearly polarized when passed through certain crystals
The arrangement of molecules in the crystal determines the direction in which the electric fields are polarized

9. Transmission axis- line along which light is polarized for a substance that polarizes light by transmission
Only light waves that are linearly polarized along the transmission axis can freely pass through the substance
All light that is polarized at an angle of 90 degrees to the transmission axis does not pass through
The light is brightest when its plane of polarization is parallel to the transmission axis
Light can be polarized by reflection and scattering

11. Surface parallel to the ground- the light is polarized horizontally
When light is reflected at a certain angle from a surface, the reflected light is completely polarized parallel to the reflecting surface
Surface parallel to the ground- the light is polarized horizontally
Glaring light reflecting at a low angle from roads, bodies of water, and car hoods
Polarizing sunglasses filter out the glare caused by horizontal polarization by having a transmission axis oriented vertically.

12. When an unpolarized beam of sunlight strikes air molecules, the electrons in the molecules begin vibrating with the electric field of the incoming wave
Horizontally polarized waves are emitted by the electrons as a result of their horizontal motion
Vertically polarized waves are emitted parallel to the Earth as a result of their vertical motion

13. Refraction
Refraction- the bending of a wave front as the wave front passes between two substances in which the speed of the wave differs
Angle of refraction, Өr- Angle in between the refracted ray and the normal
Angle of incidence- Өi
Refraction occurs when light’s velocity changes
When light moves from one medium to another, some is reflected and some is refracted

14. When a light ray moves from air into glass, refracted part is bend TOWARD the normal
Light ray moving from glass to air is bent AWAY from the normal.

15. Characteristics
Examples of transparent media: Glass, ice, water, diamonds, and quartz
If the incident ray of light is parallel to the normal, then no refraction (bending) occurs
The frequency of the light does NOT change from one medium to another

16. Need to know
Index of refraction- the ratio of the speed of light in a vacuum to the speed of light in a given transparent medium
Index of Refraction: n=c/v index of refraction=(speed of light in vacuum) divided by (speed of light in medium)
The index of refraction is a dimensionless number that is always greater than 1 since light always travels slower in a substance than in a vacuum
The larger the index of refraction is, the more refraction occurs.

17. Refraction causes objects to look like they are in different positions
Wavelength affects the index of refraction
The amount that light bends when entering a different medium depends on the wavelength of the light and the speed
A spectrum is produced when white light passes through a prism
Each color of light has a different wavelength and is refracted by a different amount

18. Snell’s Law Willebrord Snell developed Snell’s Law in 1621
Used to find the angle of refraction for light traveling between any two media
Snell’s Law: ni sinӨi = nr sinӨr index of refraction of first medium x sine of the angle of incidence = index of refraction of second medium x sine of the angle of refraction