Physics 2 Exam 2

superposition

the net displacement caused by a combination of each wave individually, can be constructive or destructive

constructive interference

waves add to a larger displacement, waves are in phase and give a larger amplitude or when waves are out of phase light becomes more intense

destructive interference

net displacement is reduced, half a wavelength is out of phase, absence of light

Huygens principle

each of the two slits in Young’s experiment acs as a source of light waves propagating outward in all forward directions, light from the two sources can overlap, resulting in an interference pattern

the angle of a bright or dark fringe

determined by the wavelength of the light and the separation of the slits

linear position of fringe on screen

determined by the distance from the slits to the screen

the separation of fringes

directly related to the wavelength of the light

difraction grating

series of many narrow lines or slits on a flat surface, an extension of the double slit experiment

more slits

peaks become narrower and more intense

….the fringes grow farther apart

as slit spacing decreases….

no change in phase

light reflecting from a medium with a lower index of refraction

phase change by half a wavelength

light reflects form a medium with a larger index of refraction

air wedge

interference fringes are regularly spaced, waves that reflect from objects at different locations can interfere with another, just like the light from two different slits 

newtons rings

system similar to an air wedge, but with a slightly different geometry. fringes become more closely spaced as one moves farther from one the center of the pattern, can be used to test the shape of a lens 

resolve

the ability to distinguish between different sources of light depends on the wavelength, the greater the wavelength the less the ability 

rayleighs criterion

if angular separation between two sources is not great enough, their diffraction patterns overlap to the point where they apear as a single elongated source

electrostatic

slow moving or stationary electric charges, proportional to the magnitudes of charges of interacting objects 

charge transfer

when two electrically neutral pieces rub together, they transfer charges from one to the other to give each piece a charge of equal magnitude but oppositesign

law of conservation of charge

the total electric charge of the universe is constant, no physical process can result in the increase or decrease in total amound of electric charge in the universe

insulators

valence electrons are tightly bound

coulombs law

the electrostatic forces exerted by two charges on each other are dependent on distance of charges and sign of charges 

positive at origin

electric field is directed outward

negative at origin

electric field is directed inward

light reflecting from medium with lower refraction index

now change in phase

light reflects from a medium with a larger index of reflection

phase changes by half a wavelength

thin films

swirling colors (like soap bubbles) created by interference (constructive and destructive) that eliminates certain wavelengths from reflected light while enhancing others.

thin films appearance depends on

colors that are removed or enhanced at given point depends on precise thickness of the film at that region

gravitational force

proportional to the masses of interacting objects