Experiment 3: Double Slit Experiment

Written By Jack Blaha

Experiment Title: Double Slit Exper

Experiment Description

The double slit experiment is a famous experiment which proved particle-wave duality of light. Originally light was thought to be particles called photons. This model made sense and worked for a long time but in 1801 the Double slit experiment proved that the particle model was actually false. The experiment has a laser or concentrated beam of light that if fired towards two slits of equal width, the light will create light and dark fringes on the other side. By treating light as a wave the double slit experiment makes a lot of sense. Huygens-Fresnel principle states that every point on a wavefront is itself the source of spherical wavelets that expand in every direction from the point of origin. Constructive interference is when the peak of a wave meets the trough of a wave, canceling out the waves. The two really small slits create two wavelets of the light (this is under the presumption that light is a wave) and at certain distances the two wavefronts constructively interfere and that creates the fringes of no light; those waves also construct on each other when two peaks or troughs meet, creating the bright fringes. There are also equations for calculating the predicted distance of fringes but those will be shown in the video.

Notes:

  • Proves particle-wave duality of light

  • Light initially thought to be particles (photons)

  • Double slit experiment in 1801 proved particle model false

  • Laser or concentrated beam of light fired towards two slits of equal width

  • Light creates light and dark fringes on the other side

  • Treating light as a wave makes sense in the double slit experiment

    • Huygens-Fresnel principle: every point on a wavefront is the source of spherical wavelets

    • Constructive interference: peak of a wave meets trough, canceling out waves

  • Two small slits create two wavelets

    • Constructive interference creates fringes of no light (dark fringes)

    • Constructive interference also creates bright fringes

  • Equations for calculating the predicted distance of fringes will be shown in the video.

Instructions

  1. Tools:

    1. Laser pointer

    2. diffraction grid

  2. Mount grid

  3. Mount laser and fire through grid

  4. Observe diffractions from the grid

Jack Blaha
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Experiment 2: Prince Rupert's Tear Drop