Physics Waves Flashcards

Amplitude (of a wave)

The maximum displacement of particles of the medium from their mean positions during the propagation of a wave.

Antinodal lines

Lines of constructive interference.

Antinode

A point of maximum amplitude because of constructive interference of waves.

Apparent frequency

Observed frequency of a wave when the source or observer is moving (f').

Beat

A kind of interference that occurs when two sets of waves have slightly different frequencies (fb = f2 - f1).

Beat frequency

Difference between the frequencies of two similar waves.

Closed Pipe

A pipe with one end open and the other end blocked up.

Compression

A part of a longitudinal wave in which the density of the particles of the medium is higher than the normal density.

Constructive interference

Two waves arriving at the same place, at the same time and in phase, add amplitudes to create a wave with a larger amplitude.

Crest

The point of maximum positive displacement on a transverse wave.

Cycle

A complete vibration.

Damped

Vibrations which gradually die out as their source loses energy.

Decibel scale

A nonlinear scale of loudness based on the ratio of the intensity level of a sound to the intensity at the threshold of hearing.

Destructive interference

Two waves arriving at the same point at the same time out of phase add their amplitudes to create zero total disturbance.

Deviates

When a wave changes direction.

Diffraction

Bending of waves around a barrier or through a gap.

Diffraction grating

Series of fine slits or lines used to deviate waves (e.g., light).

Dispersion

Refraction in e.g. a prism causes white light to split up into colours.

Doppler effect

An apparent shift in the frequency of a wave due to relative motion between the source of the wave and the observer.

Echo

A reflected sound that can be distinguished from the original sound, usually arriving at least 0.1 s after the original sound.

Emission spectra

Atomic line spectra given off from low pressure gas excited by heat or electricity.

Frequency

The number of waves which reach an observer in one second.

Fundamental

The simplest standing wave the medium can produce; the lowest possible frequency.

Harmonic

An exact multiple of the fundamental frequency (e.g., the second harmonic has twice the fundamental frequency).

Hertz

Unit of frequency; equivalent to one cycle per second.

Incandescent

Matter emitting visible light as a result of high temperature (e.g., a light bulb or flame).

Incoming waves

Waves about to collide with a boundary or interface.

Infrasonic

Sound waves having too low a frequency to be heard by the human ear (less than 20 Hz).

Intensity

A measure of the energy carried by a wave.

Interface

Boundary between two different media.

Interference

Effect occurring when waves meet.

Longitudinal wave

A wave in which the particles oscillate in the same direction as the direction of propagation (e.g., sound waves).

Loudness

Related directly to the amount of energy of the vibrating source.

Luminosity

The total amount of energy radiated into space each second from the surface of a star.

Luminous

Objects that produce visible light (e.g., stars, light bulbs, burning materials).

Mechanical wave

A wave that needs a material medium for propagation (e.g., sound waves, water waves).

Nodal lines

Lines of destructive interference.

Node

A point in a stationary wave without any disturbances where destructive interference occurs.

Noise

Sounds made up of groups of waves of random frequency and intensity.

Open Pipe

A pipe with both ends open.

Oscillation

A vibration or regular pattern of movement or compressions.

Period (of a wave)

The time required for one complete cycle of a wave.

Phase change

When a wave collides with an interface, the reflected wave has the same speed and amplitude as the incident wave but is upside down.

Pitch

Common term for the frequency of sound.

Pulse

A wave of short duration confined to a small portion of the medium at any given time.

Rarefaction

A part of a longitudinal wave in which the density of the particles is less than the normal density.

Red shift

Shift in spectral lines from stars due to their relative motion.

Reflected ray

A line representing the direction of motion of light reflected from a boundary.

Reflection

The change when light, sound, or other waves bounce backwards off a boundary.

Resonance

Oscillation when the frequency of forced vibration is the same as the natural frequency.

Reverberation

Apparent increase in volume caused by reflections, usually arriving within 0.1 seconds after the original sound.

Slit

A gap or aperture.

Sonic boom

Sound waves that pile up into a shock wave when a source travels at or faster than the speed of sound.

Sound waves

Longitudinal waves that require a medium, traveling at 340 m/s in air.

Spectrum

The dispersion of white light into its component colours (ROYGBIV).

Standing waves

Produced when two waves of equal frequency traveling in opposite directions meet.

Superimposed

When two or more waves occupy the same position at the same time, overlapping to show a combined pattern.

Superposition of pulses

Addition of wave pulses.

Thermal radiation

Electromagnetic waves with frequencies in the infrared range lower than the red end of the visible spectrum.

Time Period (of an oscillation)

The time taken to complete one oscillation.

Transverse wave

A wave in which the particles of the medium oscillate in a direction perpendicular to the direction of propagation.

Trough

The point of maximum negative displacement on a transverse wave.

Ultrasonic

Sound waves too high in frequency to be heard by the human ear (frequencies above 20,000 Hz).

Wave

A disturbance or oscillation that moves through a medium.

Wave crest

The top of the wave.

Wave front

Points on a wave where waves have the same path length from the source.

Wave motion

Movement involving the transfer of energy but not the transfer of matter.

Wave velocity

The distance travelled by a wave in one second.

Wavelength

The distance between the two nearest points on a wave (two adjacent crests or two adjacent troughs).