Waves and Particle Nature of Light

Amplitude

A wave’s maximum displacement from the equilibrium position

Frequency (f)

The number of complete oscillations passing through a point per second

Period (T)

The time taken for one full oscillation

Speed (v)

The distance travelled by the wave per unit time

Wavelength (λ)

The length of one whole oscillation

Wave equation

v=fλ

Longitudinal waves

The oscillation of particles is parallel to the direction of energy transfer

Transverse waves

The oscillations of particles is perpendicular to the direction of energy transfer

Phase

The position of a certain point on a wave cycle. This can be measured in radians, degrees or fractions of a cycle

Phase difference

How much a wave lags behind another wave

Path difference

The difference in distance travelled by two waves

Superposition

Were the displacements of two waves are combined as they pass each other, the resultant displacement is the vector sum of each wave’s displacement

Coherence

A coherent light source has the same frequency and wavelength and a fixed phase difference

Wavefront

A surface which is used to represent the points of a wave which have the same phase

Constructive interference

Occurs when two waves are in phase, their displacements are added

Destructive interference

Occurs when two waves are out of phase, their displacements are subtracted

Standing waves

Formed from the superposition of 2 progressive waves travelling in opposite directions in the same plane, with the same frequency, wavelength and amplitude. No energy is transferred

Standing wave formation on a string

A wave generated by an oscillator at one end is transferred to the other end and then reflected back, causing the superposition of two waves. Because the waves are coherent, a standing wave is formed

Refractive Index

A property of a material which measures how much it slows down light passing through it