# Sight and Wave phenomena (not resolution or diffraction)

Flashcards by Joel Hjertén , updated more than 1 year ago
 Created by Joel Hjertén over 7 years ago
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## Resource summary

 Question Answer Basic strucure of the eye Depth of vision Ability to see in 3D, enables us to judge how far away things are. Much based on experience. 2 eyes = 2 images (slightly different) -> brain can judge distance/motion better. Accomodation Distant object = ciliary muscles relax, lens gets longer and thinner Near objects = ciliary muscles contract, lens gets shorter and thicker Function of rods Scotopic vision - No colors, dim light, motion Peripheral vision - corner of our eyes Located a few degrees from the foeva and then spread out with decreasing concentration Function of cones Photopic vision - color, normal light conditions Visual acuity - ex: reading very small letters Located directly in the foeva/yellow spot which consists only of cones Primary colors Red, green, blue Secondary colors Magenta, yellow, cyan R+G = yellow G+B = Cyan R+B = Magenta Perception of colors Blue = cold Red = warm Standing waves - when do they happen? Two waves: Same frequency, same speed, nearly same amplitude, in opposite directions. They meet up and superpose. Can also happen when a wave is reflected of a fixed boundary Nodes and antinodes Node = no movement Antinode = highest amplitude Standing waves VS travelling waves Travelling waves transfer energy, standing waves do not. Any given point on a travelling wave can attain any amplitude. Wavelength of a standing wave Twice the distance between nodes/antinodes Define the Doppler Effect An effect of relative motion between a source of waves and the observer. The result is a difference between the observed freq. and the actual freq. The relation between frequency and wavelength that are Doppler shifted Low frequency = long wavelenth High frequency = short wavelength How the Doppler Effect is used to measure speed Ex: Police radars direct microwaves of known frequency at a car that is speeding. The microwaves reflect back and are Doppler shifted. The speed of the car is found by the equation at the left bottom of p.224. Define polarized light Light waves in which the oscillations only occur in one plane. What kind of waves can be polarized? Only transverse waves, not longitudal. Polarization by reflection (define) Whenever light is reflected it is partially plane polarized. Natural light is partially polarized when it passes through the atmosphere. Brewster's Law If a ray light is incident on the surface of a transparent medium so that the reflected ray is perpendicular to the refracted ray, the reflected wave will be plane polarized. Polarizer and analyzer Two sheets of polarizing material or polaroids are arranged so that they are mutually perpendicular then no light can pass through the combination. The first sheet is called the polarizer and the second the analyzer. Optically active substances A material that rotates the plane of incident plane polarized light is said to be "optically active". Some rotates clockwise, some anticlockwise. Polarization to determine concentration of solutions Depending on the concentration, the liquid polarizes less or more light. By comparing the difference in light sent through one can determine the concentration. Liquid-crystal displays (LCDs) They twist/untwist depending on the strength of the field. A reflector is at the back of the display and when no voltage is applied to the electrodes, light simply reflects right back. When the display is switched on, liquid-crystal molecules untwist and block the light.

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