Waves definitions

Question 1

amplitude

Answer 1

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

Question 2

antinode

Answer 2

point of maximum amplitude on a stationary wave

Question 3

coherent

Answer 3

two sources of waves are coherent if they emit waves with a constant phase difference

Question 4

critical angle

Answer 4

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.

Question 5

cycle

Answer 5

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.

Question 6

diffraction

Answer 6

spreading of waves on passing through a gap or near an edge

Question 7

diffraction grating

Answer 7

a plate with many closely-ruled parallel slits on it

Question 8

dispersion

Answer 8

splitting of a beam of white light by a glass prism into colours.

Question 9

electromagnetic wave

Answer 9

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.

Question 10

endoscope

Answer 10

optical fibre device used to see inside cavities.

Question 11

first harmonic

Answer 11

Pattern of stationary waves on a string when it vibrates at its lowest possible frequency.

Question 12

frequency

Answer 12

the number of cycles of a wave that pass a point per second.

Question 13

interference

Answer 13

Formation of points of cancellation and reinforcement where two coherent waves pass through each other.

Question 14

laser

Answer 14

Device that produces a parallel coherent beam of monochromatic light.

Question 15

longitudinal waves

Answer 15

Waves in which the particles oscillate parallel to the direction of energy propagation of the waves.

Question 16

modal dispersion

Answer 16

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.

Question 17

node

Answer 17

Fixed point in a stationary wave pattern where the amplitude is zero.

Question 18

optical fibre

Answer 18

A thin flexible transparent fibre used to carry light pulses from one end to the other.

Question 19

path difference

Answer 19

The difference in distances from two coherent sources to an interference fringe.

Question 20

period

Answer 20

Time for one complete cycle of a wave to pass a point.

Question 21

phase difference

Answer 21

The fraction of a cycle between the vibrations of two vibrating particles, measured either in radians or degrees.

Question 22

plane-polarised waves

Answer 22

Transverse waves that vibrate in one plane only.

Question 23

progressive waves

Answer 23

Waves which transfer energy from one place to another.

Question 24

refraction

Answer 24

Change of direction of a wave when it crosses a boundary where its speed changes.

Question 25

refractive index

Answer 25

ratio of speed of light in vacuum to speed of light in the substance

Question 26

stationary waves

Answer 26

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.

Question 27

superposition

Answer 27

When two waves meet and their displacements add.

Question 28

total internal reflection

Answer 28

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.

Question 29

transverse waves

Answer 29

waves in which the oscillations are perpendicular to the direction of propagation of energy of the waves

Question 30

wavefronts

Answer 30

lines of constant phase (e.g., wavecrests)

Question 31

wavelength

Answer 31

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).

Question 32

Young’s fringes

Answer 32

Parallel bright and dark fringes observed when light from a narrow slit passes through two closely spaced slits and interferes.