Electrons, Waves and Photons: Waves

Flashcards covering the fundamental concepts of waves, including wave types, descriptions, mathematical relationships (Intensity, Frequency, Wave Speed), phase differences, and the principle of superposition.

Waves

The transfer of energy from place to place without transferring the material they move through.

Progressive Wave

An oscillation that travels through matter or a vacuum, transferring energy from one place to another but not matter.

Transverse Wave

A wave where the particles vibrate at $90^\text{o}$ to the direction of the energy transfer.

Longitudinal Waves

Often called compression waves, these are waves where the particles vibrate parallel to the direction of energy transfer.

Compressions and Rarefactions

A series of regions created when longitudinal waves travel through a medium where particles are either close together (compressions) or spread apart (rarefactions).

Propagation

The direction in which energy is transferred.

Displacement ($d$)

The distance from the equilibrium position in a particular direction.

Amplitude ($A$)

The maximum displacement from the equilibrium position in a particular direction.

Time period ($T$)

The time taken for one complete oscillation.

Frequency ($f$)

The number of complete oscillations per second, calculated as $f = \frac{1}{T}$, measured in Hertz ($Hz$) or $s^{-1}$.

Wavelength (\text{\lambda})

The minimum distance between two points which oscillate with the same phase.

Wave Speed ($v$ or $c$)

The distance travelled by the wave per unit time, governed by the equation v = f\text{\lambda}.

Oscilloscope

A device used to determine the frequency of a wave by showing a graph of p.d. against time using settings like y-gain ($V/div$) and Time base ($ms/div$).

Intensity ($I$)

The radiant power passing through a surface per unit area, measured in $W m^{-2}$ and calculated as $I = \frac{P}{A}$.

Intensity from a Point Source

The radiant power spreads uniformly over the surface of a sphere, calculated as I = \frac{P}{4\text{\pi}r^2}.

Intensity and Amplitude Relationship

A relationship where intensity is directly proportional to the square of the amplitude (I \text{\propto} A^2).

In-phase

Two particles that have the same exact displacement and are moving in the same direction at the same time.

Phase Difference

Tells you how much a wave/particle is in front of or behind another, written as an angle in degrees ($360^\text{o}$ for one wavelength) or radians (2\text{\pi} for one wavelength).

Anti-phase

A phase difference equivalent to $180^\text{o}$ or \text{\pi} radians.

Superposition

Occurs when two waves pass through the same region of space and overlap, temporarily forming a new wave.

Principle of Superposition

States that where two waves meet, the sum of their displacements add vectorally.