Wave Theory of Light Chapter 9 SPH4U1

ray approximation

pretending that light moves in straight parallel lines

law of reflection

angle of incidence = angle of reflection

refraction

the bending of light as it passes from one medium to another

principle of reversibility

a path a light ray follows remains the same if its direction of travel is reversed

optical density

tendency to absorb energy of electromagnetic waves

higher optical density = slower speed of wavelength

index of refraction

ratio of the speed of light in a vacuum to the speed of light in a medium.

n = c/v

what is the index of refraction affected by

different substances and different wavelengths

snells law

n1sin01 = n2sin02

formula for wavelength from snells law

n2/n1 = λ1/λ2

dispersion

is the separation of light into its component colors due to varying indices of refraction for different wavelengths.

total internal reflection

angle of incidence surpasses critical angle resulting in no refracted ray and the ray is totally reflected at the boundary

critical angle

smallest angle where light stops refracting and begins to reflect. when the angle of refraction, or 02, is 90 degrees

equation to find critical angle

sin0c = n2/n1

diffraction

bending of a wave as the wave passes through an opening or by an obstacle

what does diffraction depend on

size of opening and wavelength of wave

diffraction analysis equation

in order for noticeable diffraction…

λ >= w or

λ/w >= 1

relationship between λ and diffraction

as wavelength increases, diffraction increases

relationship between size of slit and diffraction

as size of slit decreases, diffraction increases

*if λ remains constant

interference

two waves in the same medium interacting

constructive interference

two waves adding together to create a wavelength with greater amplitude

crest to crest or trough to trough

destructive interference

who waves subtract to create wave w smaller amplitude or cancel out

crest to trough

node

point where destructive interference occurs ersulting in 0 amplitude and 0 displacement

nodal lines

lines of 0 displacement

coherent waves

same frequency and fixed phases

conditions for interference

Must be coherent, come from common area, two or more waves

huygens’ principle

alll points on a wave front can be through of as new sources of spherical waves

drawbacks of wave theory of light

requires invisible ether to travel through
waves spread out, while light moves in a straight line