Particle and Wave Models of Light

Flashcards about the particle and wave models of light.

Galileo's Contribution (1638)

Galileo attempted to measure the speed of light using lamps and assistants, concluding that light, if not instantaneous, is extraordinarily rapid, at least 10 times faster than sound.

Ole Roemer's Discovery (1675)

Danish astronomer Ole Roemer observed variations in the timing of Jupiter's moon eclipses, deducing that light travels at approximately 2 x 108 m/s.

Armand Hippolyte Louis Fizeau's Experiment (1849)

Fizeau used a rotating toothed wheel and a mirror to measure the speed of light at 3.133 x 108 m/s.

Jean Bernard Leon Foucault's Experiment (1862)

Foucault refined Fizeau's method using rotating mirrors, measuring the speed of light at 2.99796 x 108 m/s.

Albert Michelson's Experiment

Michelson improved accuracy using rotating mirrors and long distances (35 km between mirrors on mountains) to measure the speed of light.

Modern Measurement of Light Speed

The current accepted value for the speed of light is 2.99792458 x 108 m/s, which is exact because the meter is defined based on this constant and the international standard for time.

Constructive Interference

Occurs in microwaves at hotspots, specifically at 1/2λ, due to waves following the same paths repeatedly.

Newton’s Particle Model of Light

Light travels in straight lines and light is shot out from a source as a stream of particles.

Evidence Against the Particle Model - Diffraction

If light is a particle then it will not be able to diffract after going through an opening or around an obstacle.

Huygens’ Wave Model of Light

Huygens proposed that the ether must fill all space, be transparent and of zero inertia.

Diffraction

The amount of diffraction is dependent upon the relationship between the opening size and wavelength.

Light as an Electromagnetic Wave

Oscillating electric charge produces sinusoidally varying electric and magnetic fields

Photoelectric Effect

When metal surfaces are exposed to an ultraviolet light, negative charges are emitted from the metal.

Einstein's Particle Model Prediction

Individual photons knock out electrons and that only photons with enough energy (above the threshold frequency) can do this.

Principle of Complementarity

A complete understanding requires a description of both wave and particle properties.