Wave Properties Wave Properties of Lightof Light

Characterization of LightCharacterization of Light Light has both a wavelike and particle Light has both a wavelike and particle

like nature.like nature.

Electromagnetic wave theoryElectromagnetic wave theory: Light is a : Light is a wave composed of oscillating electric and wave composed of oscillating electric and magnetic fields (magnetic fields (electromagnetic waveelectromagnetic wave).).

These waves propagate transversely at These waves propagate transversely at right angles to each other.right angles to each other.

Oscillating Oscillating Magnetic Magnetic FieldField

Oscillating Oscillating Electric FieldElectric Field

Characterization of LightCharacterization of Light

All electromagnetic waves travel at All electromagnetic waves travel at the speed of light (c). the speed of light (c).

c = 3.0 x 10c = 3.0 x 1088 m/s m/s

Electromagnetic waves vary Electromagnetic waves vary depending on frequency and depending on frequency and wavelength.wavelength.

These differences account for the These differences account for the broad range in the electromagnetic broad range in the electromagnetic spectrum.spectrum.

Characterization of LightCharacterization of Light

Electromagnetic Electromagnetic SpectrumSpectrum

The same relationship between The same relationship between frequency, wavelength, and speed frequency, wavelength, and speed that exists in sound waves or that exists in sound waves or objects undergoing SHM also holds objects undergoing SHM also holds true for electromagnetic waves. true for electromagnetic waves.

Characterization of LightCharacterization of Light

νν = = f f λλ (classic wave (classic wave

speed equation)speed equation)

c = c = f f λλ

Huygen’s PrincipleHuygen’s Principle

Electromagnetic waves travel in Electromagnetic waves travel in wave fronts.wave fronts.

Wave fronts are made up of many Wave fronts are made up of many wavelets, each containing a “point wavelets, each containing a “point source”. If you make a line tangent source”. If you make a line tangent to each point source, you have to each point source, you have identified a new wave front.identified a new wave front.

Characterization of LightCharacterization of Light

Characterization of LightCharacterization of Light Huygens Huygens Principle describe Principle describe waves interacting waves interacting with matter with matter (diffraction) or (diffraction) or waves moving in a waves moving in a straight line.straight line.

The The perpendicular perpendicular direction in which direction in which the wave front is the wave front is moving is referred moving is referred to as ato as a “ray”.“ray”.

Wave front motion as it moves Wave front motion as it moves around an objectaround an object

Characterization of LightCharacterization of Light

What is the relationship between brightness and the

distance from a light source?

Light becomes more spread out Light becomes more spread out and there is less light available per and there is less light available per unit area.unit area.

Brightness decreases by the square Brightness decreases by the square of the distance from the source.of the distance from the source.

Inverse square relationshipInverse square relationship

ex. There is ¼ as much light falling on a ex. There is ¼ as much light falling on a particular spot 2 m away than there is light particular spot 2 m away than there is light falling on the same spot that is 1 m away.falling on the same spot that is 1 m away.

Characterization of LightCharacterization of Light