Optics 3 Lecture 9 Wave Properties and Superposition

Light is an ____ radiation

Electromagnetic radiation

The electric and magnetic fields are

perpendicular to each other

perpendicular to the direction of propagation

emitted from as souce and carried through space

A wave is a _____ in a medium

"periodic" disturbance

(also propagating disturbance)

a regular transfer of energy through a medium

must being at a source

propagates away from the source

a receive can detect this distrubtion and receive energy and momentum carried by the ayve

rectilinear propagation

path of light travel in a STRAIGHT LINE

if there is nothing between the two pints there is no reason for rays to change direction

The disruption though the medium ______ change the medium

does not change

think wave at a stadium .... we all end where we started

oscillation

the direction of movement of the molecules

propagation

the direction of travel of the wave

transverse wave

oscillation and propagation are perpendicular to each other: in the opposite direction

(stadium wave)

Longitudinal wave

oscillation and propagating are parallel to each otherL in the same direction

slinky or sound wave

crest

highest point of the eave

trough

lowest point of the wave

Amplitude

maximum displacement from a reference line

Highest point of crest (+A)

lowest point of the rough (-A)

louder / brighter =

greater amplitude

softer / dimmer

lesser amplitude

Wavelength

distance for one full cycle/ one full oscillatino

measured from crest to crest or trough to trough

units: nm

Frequency

number of oscillations or cycles per second

units: Hertz (Hz) or cyles/sec or s-1

Period (T)

time it takes for one full oscillation / one full cycle

inverse of frequency

units: seconds/cycle

increase wavelength , frequency will

decrease

wavelength decreases, frequency will

increase

___ will determine the pitch

frequency

higher frequency (shorter wavelength) = ____ pitch

high pitch

Low frequency (longer wavelength) = _____ pitch

low pitch

____ will affect the color

wavelength

Longer wavelength (shorter frequency) =

red/ orange

Shoter wavelength (higher frequency) =

green / blue

in air (a vacuum) the speed of light is

c = 3 x 10^8 m/s

velocity =

wavelength x frequency

Inverse relationship!

The _____ of the light will be different in the medium the light entered as compared to the medium that the light came from

velocity and wavelength

_____ of the medium affects the properties of light the most

index of refraction

Low --> high index

Velocity slows down

wavelength decreases

frequency stays the same

Any material other than air, the speed of light will always be

less than 3 x 10^8 m/s

Refractive index ratio

Velocity in air/ velocity in the material

wavelength in air/ wavelength in material

ALWAYS AIR ON TOP

____ stays the same as we change mediums

Frequency!

Why does color not change when we are in a new medium?

our eyes are sensitive to frequency not wavelength

Linear velocity

a distance traveled over a unit time

the distance along the x-axis

Because we think of out wave as sine or a cosine, it is considered top be

harmonic

Sine and cosine wave can be thought of

as an unfolded circle

tracing the distance of one fuill wave cucle is equal to tracing the distance around a cirle

angular velocity

rate of change of angular displacement

Radian

an arc of a circle with the same length as the radius of that circle subtends an angle of 1 radian

Radian to degrees conversion

pi radians = 180 degrees

90 degrees = pi/2 radians

270 degrees = 3pi/2 radians

360 degrees = 2pi radians

see graphs please

sine wave

Starts at 0, crosses at 180 + 360

cosine wave

peak at zero

crosses at 90 and 270

Phase angle (angle phi)

Any position (in radians) of out wave

The amplitude of a wave is proportional to its

intensity I = A^2

Intensity of a wave

energy delivered per unit area per unit time

represents our perception of the amplitude of the wave

Brightness or loudness

interference

the way in which 2 light waves interact or combine with each other

Constructive interference

greater than the sum of its parts

Destructive interference

less than the sum of its parts

Neither constructive or destructive

equal to the sum of its parts

Phase shift

the position of one wave relative to another that it will be interfering with

delta phi

In phase waves will lead to

constructive interference

Partially in phase waves lead to

constructive interference but not as great if they were perfectly in phase

Out of phase relsults in

destructive interference

partially out of phase will lead to

destructive interference but not as less as perfectly out of phase

Total constructive interference

maximized brightness

could not be any more in phase

Total destructive interference

occurs when the waves are perfectly out of phase --> 180 degrees or pi rad AND intensities of each individual wave are the same

total darkness

resultant intesnsity of 0

Waves that are perfectly out of phase result in total destructive interfernce WHEN

WHEN the individual wave intensities are EQUAL

Waves that are perfectly out of phase result in partial interference WHEN

the intensities are not equal

If the interference term is plus

constructive

If the interference term is minus

destructive

If the interference term is zero

neither

Coherent waves

the phase shift between the waves is consisten

the deffernce in phase doesnt change as the wave travels

angular velocity is constanc

incoherent waves

the phase shift between the waves is inconsistent

the difference in phase continually changes randomly as the wave travels

angular velocity for one or both waves changes