Light Light Interference & Interference & the Double Slit the Double Slit ExperimentExperiment

By Zach Schmidt By Zach Schmidt

& Neekaan Oshidary& Neekaan Oshidary

Light: A Particle or WaveLight: A Particle or Wave

Different tests support different Different tests support different sides of the argumentsides of the argument

Today: dual theoryToday: dual theory Young ExperimentYoung Experiment

Double Slit AnalogyDouble Slit Analogy

Particles Through One SlitParticles Through One Slit

Particles Through Both Particles Through Both SlitsSlits

Interference or Not?Interference or Not?

The ExperimentThe Experiment

Components:Components:Light Source: Lasers Light Source: Lasers Double Slit: Pre-made slitsDouble Slit: Pre-made slitsDetector: Smooth surfaceDetector: Smooth surface

INTERFERENCE!INTERFERENCE!

Testing VariablesTesting Variables

Distance and Fringe WidthDistance and Fringe Width

w/D=C, DIRECTw/D=C, DIRECT WhereWhere w= fringe widthw= fringe width

D= distance between slits and detectorD= distance between slits and detectorC= constantC= constant

Fringe Width vs. Distance for Slit Seperations

0

5

10

15

20

1 2 3 4

Distance (m)

Fri

ng

e W

idth

(m

m)

0.176 mm

0.35 mm

0.7 mm

Slit Separation and Fringe Slit Separation and Fringe WidthWidth

w w xx s=C, INVERSE s=C, INVERSE WhereWhere w= fridge width w= fridge width

s= slit separations= slit separation

C= constantC= constant

Understanding Inverse Understanding Inverse relation of slit separation relation of slit separation and fringe width.and fringe width.

Wavelength and Fringe Wavelength and Fringe WidthWidth

w/w/C, DIRECTC, DIRECT WhereWhere w=fringe widthw=fringe width

wavelengthwavelength

C= constantC= constant

Recap of relationshipsRecap of relationships

w/D=C, Distance: directw/D=C, Distance: direct w*s=C, Slit separation: inversew*s=C, Slit separation: inverse w/w/=C, Wavelength: direct=C, Wavelength: direct Can we combine these into one larger Can we combine these into one larger

equation?equation?

What about Wavelength?What about Wavelength?

(S (S x x W)/DW)/D

ResultsResults

Helium-neon laserHelium-neon laser Our calculation: 610.5 nmOur calculation: 610.5 nm Real value: 632.5Real value: 632.5 Percent Error: 3.5%Percent Error: 3.5%

Particle Nature of LightParticle Nature of Light

Light consists of bundles of energy Light consists of bundles of energy called photonscalled photons

What would happen if we slowed What would happen if we slowed down the laser, so only one photon down the laser, so only one photon at a time arrived at the slits?at a time arrived at the slits?

Does This Make Any Does This Make Any Sense?Sense?

ConclusionConclusion

Light behaves like a wave; Light behaves like a wave; interferenceinterference

We used this property to calculate We used this property to calculate the wavelength of lightthe wavelength of light

Light also behaves like a particleLight also behaves like a particle This behavior is described in the This behavior is described in the

dual wave/particle theorydual wave/particle theory

THE END!THE END!