Waves - Double Slit Experiment & Electromagnetic Waves

if light behaves like a wave., it should have

dark areas (DI) and bright areas (CI)

young experiment involved a

• monochromatic light

• narrow slits (one in front, two after that)

• the light leaving the double slits acted as 2 sources and was essentially IN PHASE and exhibited the same wave properties

interference of light waves visual

the bands of bright bands are otherwise refered to as

• maxima (CI)

• interference fringe

the bands of dark bands are otherwise refered to as

• minima (DI)

• interference fringe

to det the wl of the light, you have to first det the

path length difference between each slit and the screen.

the bands were created on the screen bc

of the light waves diffracting from going thru the small slit

zero-order maxima

the central maxima

the eqn with m is for

maximas

maximas occur at the location given by that eqn w the sin function

m =

0,1,2,3 → 0 would be the central maxima and the maxes are counted outwards

• this is where CI happens

to get DI, the second wave len must trav

an extra dist behind or in front of the other wave to reach the screen

→ must be a mult of wl/2 but cannot bea whole number

to find where minimas occur

use the formula w (n - 1/2), wl, d, and sin func (see notes)

where n = 1, 2, 3 → first order min, second order min and so on

to calc the fringe width

the eqn w Xm and m is for bright fringes

the eqn w Xn, (n - 1/2 ) is for dark fringes

the fringe width and intensity of the fringes is

uniform

to calc the sep b/w any two adjacent fringes

use the eqn w no angle

the central fringe (zero-order max) =

2(x1)

EM waves are

complex transverse waves

• particles move in every dir that is perpen to the trajectory of trav

how EM waves work

• vibrating electric charges in space produce an electric field

• moving charges set up a magnetic field perpendicular to motion of charge

• changing magnetic field induces an electric field perpendicular to the magnetic field AND they continuously change

• interacting electric and magnetic fields will travel through a vacuum in the form of EM waves at c=3.0x108 m/s

Electromagnetic propagation

ε induces changing B, which induces changing ε, which induces changing B, and so on that are

• oscillating in phase perpendicular to each other

• and at 90° to the direction of the wave

Wave-Particle Duality

• Light energy propagates as a wave BUT when it interacts with matter behaves like a particle

• Photons are discrete bundles of energy that do not have mass and exhibit interference effects like electrons (from Einstein’s Quantum Thy of Light)

EM waves can

interfere, diffract, refract, polarize, and have linear and angular momentum

All EM waves travel through a vacuum at

c= 3.00 x 108 m/s and obey the universal wave eq’n 𝒗 = 𝒇𝝀