AS Level Physics - Waves Flashcards

Vocabulary practice flashcards for AS Level Physics - Waves covering progressive and stationary waves, interference, diffraction, polarization, Doppler effect, and key wave terminology.

Progressive Waves

Waves that travel or move and transfer energy from one point to another as they travel.

Transverse Waves

Waves in which the direction of disturbance is perpendicular to the direction in which the wave travels.

Longitudinal Waves

Waves in which the direction of disturbance or vibration is parallel to the direction in which the wave travels.

Amplitude ($A$)

The maximum displacement of a wave particle from its mean position.

Time Period ($T$)

The time taken for one complete wave or oscillation.

Wavelength ($\lambda$)

The distance between two consecutive in-phase points, such as two crests, two troughs, or two successive compressions or rarefactions.

Frequency ($f$)

The number of waves, oscillations, or cycles formed in $1\,\text{second}$, measured in Hertz ($\text{Hz}$).

Wave Speed ($v$)

The distance travelled by a wave each second, given by the formula $v = f\lambda$.

Path Difference

The gap between any two points on a wave profile expressed in terms of wavelength ($\lambda$).

Phase Difference

The gap between any two points on a wave profile expressed in terms of degrees or radians, where a path difference of $1\lambda$ corresponds to $360^\circ$ or $2\pi\,\text{radians}$.

In-Phase Points

Points on a wave profile whose behavior is exactly identical, having a path difference of $1\lambda, 2\lambda, 3\lambda, \dots$ and a phase difference of $2\pi, 4\pi, 6\pi, \dots\,\text{radians}$.

Out-of-Phase Points

Points on a wave profile whose behavior is exactly opposite, having a path difference of $\frac{1}{2}\lambda, \frac{3}{2}\lambda, \frac{5}{2}\lambda, \dots$ and a phase difference of $\pi, 3\pi, 5\pi, \dots\,\text{radians}$.

Compression ($C$)

A region in a longitudinal wave where particles are at maximum pressure and closest together.

Rarefaction ($R$)

A region in a longitudinal wave where particles are at minimum pressure and furthest apart.

Y-gain

A control on a CRO (cathode-ray oscilloscope) that changes how a wave appears vertically by determining what $1\,\text{div}$ or $1\,\text{cm}$ represents in the y-direction.

Time Base

A control on a CRO that changes how a wave appears horizontally by determining what $1\,\text{div}$ or $1\,\text{cm}$ represents in time on the x-axis.

Principle of Superposition

The principle stating that if two or more waves overlap or meet at a common point, the total displacement due to these waves is the sum of their individual displacements.

Coherent Waves

Waves that maintain a constant path difference or a constant phase difference throughout.

Constructive Interference

Interference occurring when in-phase points superimpose, resulting in increased amplitude and path differences of $1\lambda, 2\lambda, 3\lambda, \dots$.

Destructive Interference

Interference occurring when out-of-phase points superimpose, resulting in reduced or zero amplitude and path differences of $\frac{1}{2}\lambda, \frac{3}{2}\lambda, \frac{5}{2}\lambda, \dots$.

Intensity ($I$)

The power of a wave falling on a unit area ($I = \frac{P}{A}$), measured in $\text{W\,m}^{-2}$, which is directly proportional to the square of amplitude ($I \propto A^2$).

Diffraction

The spreading out of waves as they pass through a narrow gap or around an edge, which is most significant when the size of the gap is comparable to the wavelength.

Diffraction Grating

An optical device with many microscopic slits that causes incident light to diffract and produce maximums according to the grating equation $d \sin(\theta) = n\lambda$.

Fringe Separation ($x$)

The distance between two consecutive bright fringes or dark fringes in Young's double slit setup, given by $x = \frac{\lambda D}{a}$.

Polarization

The phenomenon occurring only in transverse waves where vibrations are restricted to a single direction or plane perpendicular to the direction of propagation.

Law of Malus

The relationship stating that the transmitted light intensity $I$ through a polaroid is related to incident intensity $I_0$ by $I = I_0 \cos^2(\theta)$, where $\theta$ is the angle between transmission axes.

Doppler Effect

The apparent change in the observed frequency of a wave caused by relative motion between the source of the wave and the observer.

Red Shift

The shift of observed light frequencies towards lower frequencies (red end) when a light source moves away from an observer.

Stationary Waves

Waves formed by the superposition of two progressive waves of equal frequency, wavelength, and amplitude travelling in opposite directions, resulting in no net energy transfer.

Nodes and Antinodes

Key points in a stationary wave where nodes are positions of zero displacement/amplitude and antinodes are positions of maximum displacement/amplitude.