NCEA Level 3 Physics - Waves Flashcards

Vocabulary flashcards covering the key terms and definitions for NCEA Level 3 Physics - Waves.

Amplitude

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 wave when source or observer is moving $(f')$

Beat

A kind of interference. It occurs when two sets of waves have slightly different frequencies. $f_b = f_2 - f_1$

Beat frequency

Difference between the frequencies of two similar waves

Bright fringe

Area of constructive interference

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

Dark fringe

Area of destructive interference

Decibel Scale

A nonlinear scale of loudness based on the ratio of the intensity 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

Wave changes direction

Diffraction

Bending of waves around a barrier / through a gap

Diffraction grating

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

Doppler effect

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

Dispersion

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

Echo

A reflected sound that can be distinguished from the original sound, which usually arrives at least $0.1\,\text{s}$ after the original sound

Emission spectra

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

Frequency (cycles per second)

The number of cycles per second

Fringe

Band of light/dark

Frequency (waves per second)

The number of waves which reach an observer in one second

Harmonic

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

Fundamental

This is the simplest standing wave the medium can produce. It is the lowest possible frequency

Incandescent

Matter emitting visible light as result of high temperature e.g. a light bulb/flame because of high temperature

Incident

Moving towards (e.g. incident light strikes a mirror)

Hertz

Unit of frequency; equivalent to one cycle per second

Incoming waves

Waves about to collide with boundary/interference

Intensity

A measure of the energy carried by a wave

Interface

Boundary between two different media

Interference

Effect occurring when waves meet

Longitudinal wave

The wave in which the particles oscillate in the same direction as the direction of propagation of wave e.g. sound wave

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

Infrasonic

Sound waves having too low a frequency to be heard by the human ear; sound having a frequency of less than $20\,\text{Hz}$

Mechanical wave

The wave, which needs a material for their propagation e.g. sound wave, water wave

Nodal lines

Lines of destructive interference

Node

A point in a stationary wave without any disturbances. Destructive interference

Luminous

An object or objects that produce visible light. For example star/light bulbs/burning materials

Open pipe

A pipe with both ends open

Noise

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

Period

The time required for one complete cycle of a wave

Oscillation

Vibration or regular pattern of movement or compressions e.g. sound waves in air

Pitch

Frequency of sound

Polarized light

Whose constituent transverse waves are all vibrating in the same plane

Phase change

When waves collide with an interface, the reflected wave has same speed/amplitude as incident wave but is upside down

Pulse

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

Polaroid

A film that transmits only polarised light

Red shift

Shift in spectral lines from stars due to their relative motion

Rarefaction

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

Reflection

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

Reflected ray

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

Resonance

Oscillation when frequency of forced vibration is same as natural frequency

Relativistic mass

The mass an object would have if you could measure it while it is moving

Slit

Gap/Aperture

Reverberation

Apparent increase in volume caused by reflections, usually arriving within $0.1\,\text{s}$ after the original sound

Sound wave

Longitudinal wave that requires a medium (travels at $340\,\text{m}\,\text{s}^{-1}$ in air)

Spectrum

The dispersion of white light into its component colours ROYGBIV for visible light

Standing waves

Where two waves of equal frequency travelling in opposite directions meet they can produce these

Sonic boom

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

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 (by distance)

The time taken by a wave to travel through a distance equal to its wavelength

Time period (by oscillation)

The time taken to complete one oscillation

Superimposed

When two or more waves occupy the same position at the same time, they 'overlap' and show a combined pattern

Transverse waves

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

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 $20,000\,\text{Hz}$

Unpolarised light

Light consisting of transverse waves vibrating in all conceivable random directions

Wave

A disturbance or oscillation that moves through a medium

Wave crest

Top of the wave

Total internal reflection

Occurs when a wave arrives at a boundary at the critical angle or beyond and is reflected back

Wave front

Point on wave where waves have the same path length from the source

Wave motion

The movement produced involving the transfer of energy but not the transfer of matter

Wave period

The time required for two successive crests or other parts of the wave to pass a given point

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)

Wave direction

Direction which wave is travelling (wave front will be $90\text{ degrees}$ to this)