Waves definitions Flashcards
amplitude
maximum displacement of a vibrating particle from its equilibrium position; for a transverse wave, it is the distance from the middle to the peak of the wave
antinode
point of maximum amplitude on a stationary wave
coherent
two sources of waves are coherent if they emit waves with a constant phase difference
critical angle
The angle of incidence at the which the angle of refraction is equal to 90 degrees. 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
transverse electric and magnetic waves in phase and at right angles to each other. Speed in a vacuum = 3.00 x 10^8 ms^-1.
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.
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 monochromatic light.
longitudinal waves
Waves in which the particles oscillate parallel to the direction of energy propagation of the waves.
modal dispersion
The lengthening of a 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 fibre
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 either in radians or degrees.
plane-polarised waves
Transverse waves that vibrate in one plane only.
progressive waves
Waves which transfer energy from one place to another.
refraction
Change of direction of a wave when it crosses a boundary where its speed changes.
refractive index
ratio of speed of light in vacuum to speed of light in the substance
stationary waves
Wave pattern with nodes and antinodes formed when two progressive waves of the same frequency and amplitude travelling in opposite directions pass through each other and superpose. Stationary waves do not transfer energy.
superposition
When two waves meet and their displacements add.
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 a certain value known as the critical angle.
transverse waves
waves in which the oscillations are perpendicular to the direction of propagation of energy 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 and interferes.
