Topic 3 - Waves Flashcards
Amplitude
Maximum displacement of a vibrating particle; for a transverse wave, it is the distance from the middle to the peak of the wave.
Antinode
Fixed point in a stationary wave pattern where the amplitude is a maximum.
Coherent
Two sources of waves are coherent if they emit waves with a constant phase difference.
Critical Angle
The angle of incidence of a light ray must exceed the critical angle for total internal reflection to occur.
Cycle
Interval for a vibrating particle (or a wave) from a certain displacement and velocity to the next time the particle (or the next particle) that has the same displacement and velocity.
Diffraction
Spreading of waves on passing through a gap or near an edge.
Diffraction grating
A plate with many closely-ruled parallel slits on it.
Dispersion
Splitting of a beam of white light by a glass prism into colours.
Electromagnetic wave
A wave packet or photon consisting of transverse electric and magnetic waves in phase and at right angles to each other.
Endoscope
Optical fibre device used to see inside cavities.
First harmonic
Pattern of stationary waves on a string when it vibrates at its lowest possible frequency.
Frequency
The number of cycles of a wave that pass a point per second. Measured in Hz
Interference
Formation of points of cancellation and reinforcement where two coherent waves pass through each other.
Laser
Device that produces a parallel coherent beam of monochromic light.
Longitudinal waves
Waves with a direction of vibration parallel to the direction of propagation of the waves.
Matter waves
The wave-like behaviour of particles of matter.
Modal dispersion
The lengthening of light pulse as it travels along an optical fibre, due to rays that repeatedly undergo total internal reflection having to travel a longer distance than rays that undergo fewer total internal reflections.
Node
Fixed point in a stationary wave pattern where the amplitude is zero.
Optical fibres
A thin flexible transparent fibre used to carry light pulses from one end to the other.
Path difference
The difference in distances from two coherent sources to an interference fringe.
Period
Time for one complete cycle of a wave to pass a point.
Phase difference
The fraction of a cycle between the vibrations of two vibrating particles, measured in either radians or degrees.
Plane-polarised waves
Transverse waves that vibrate in one plane only.
Progressive waves
Waves which travel through a substance or through space if electromagnetic.
Radian
Measure of an angle defined such that 2pi radians = 360 degrees
Refraction
Change in direction is a wave when it crosses a boundary where it’s speed changes.
Refractive index
Speed of light in free space / speed of light in the substance.
Spectrometer
Instrument used to measure light wavelengths very accurately.
Stationary waves
Waves pattern with nodes and antibodies formed when two or more progressive waves of the same frequency and amplitude pass though each other.
Superposition
The effect of two waves adding together when they meet.
Total internal reflection
A light ray travelling in a substance is totally internally reflected at a boundary with a substance of lower refractive index, if the angle of incidence is greater than the critical angle.
Transverse waves
Waves with a direction of vibration perpendicular to the direction of propagation of the waves.
Wavefronts
Lines of constant phase (e.g. wavecrests)
Wavelength
The least distance between two adjacent vibrating particles with the same displacement and velocity at the same time (e.g. distance between two adjacent wave peaks).
Young’s fringes
Parallel bright and dark fringes observed when light from a narrow slit passes through two closely spaced slits.
