Topic 4: Waves and Oscillations

Question 1

Oscillation

Answer 1

A repeated back and forth motion.

Question 2

Cycle

Answer 2

One complete oscillation.

Question 3

Amplitude

Answer 3

The maximum displacement from the equilibrium position

Question 4

Frequency

Answer 4

The number of oscillations completed in a second (unit is hertz, Hz)

Question 5

Displacement

Answer 5

The distance of the oscillating object measured from its equilibrium position

Question 6

Period

Answer 6

The time taken for an oscillation. f=1/T; T=1/f

Question 7

Phase difference

Answer 7

Two oscillations which are not in step have a phase difference (expressed as an angle). A phase difference of one oscillation is 2pi radians.

Question 8

Simple harmonic motion

Answer 8

A motion where the acceleration is proportional to the displacement at all times but is oppositely directed and towards equilibrium.

Question 9

Damping

Answer 9

The loss of energy of oscillations due to work against (friction or viscous medium). Can be heavy, light or critical.
Results in reduction in amplitude

Question 10

Natural frequency

Answer 10

The frequency at which a system will oscillate naturally.

Question 11

Forced oscillations

Answer 11

Oscillations of a system which is being driven at another frequency than its natural one.

Question 12

Resonance

Answer 12

When the driving oscillation has the same frequency as the natural frequency of the system, the amplitude of the system will increase.

Question 13

Travelling wave

Answer 13

A disturbance moving from a source and transferring energy from one point to another.

Question 14

Transverse wave

Answer 14

Where the direction of energy propagation is at right angles to the direction of travel of the wave.

Question 15

Longitudinal wave

Answer 15

Where the direction of energy propagation is parallel to the direction of travel of the wave.

Question 16

Wavefront

Answer 16

A line of surface which joins all points which have the same displacement at the same moment (they are all in phase).

Question 17

Ray

Answer 17

A line at right angles to the wavefronts which shows the direction of energy travel of the wave.

Question 18

Crest and trough

Answer 18

For a transverse water wave, the maximum and minimum displacements.

Question 19

Compression & rarefaction

Answer 19

For a longitudinal wave, points of maximum and minimum density of the medium.

Question 20

Wavelength

Answer 20

The distance between consecutive points on the wave which are in phase

Question 21

Wave speed

Answer 21

The speed of travel of the energy of the wave.

Question 22

Intensity

Answer 22

The rate of flow of energy through unit area perpendicular to the direction of travel of a wave. Unit: Wm-2

Question 23

Snell’s Law

Answer 23

For two particular media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant. This is also equal to the ratio of their speeds.

Question 24

Diffraction

Answer 24

The spreading of waves when they pass through an opening or round an obstacle.

Question 25

Superposition

Answer 25

When two waves pass the same point at the same time, their displacements are added together to calculate the resultant displacement.

Question 26

Interference

Answer 26

Superposition of coherent sources resulting in an interference pattern.

Question 27

Constructive/Destructive

Answer 27

Interference in which the resultant is reinforced/ cancelled.