2.5 Wave Properties

Question 1

Diffraction

Answer 1

the spreading out of waves when they meet obstacles, such as the edges of a slit. Some of the wave’s energy travels into the geometrical shadows of the obstacles.

Question 2

Wavelength of a progressive wave

Answer 2

the minimum distance (measured along the direction of propagation) between two points on the wave oscillating in phase.

Question 3

Frequency of a wave

Answer 3

the number of cycles of a wave that pass a given point in one second, [or equivalently the number of cycles of oscillation per second performed by any particle in the medium through which the wave is passing.]

Question 4

Speed of a wave

Answer 4

The speed of a wave is the distance that the wave profile moves per unit time.

Question 5

The principle of superposition

Answer 5

if waves from two sources [or travelling by different routes from the same source] occupy the same region then the total displacement at any one point is the vector sum of their individual displacements at that point.

Question 6

Phase difference

Answer 6

Phase difference is the difference in position of 2 points within a cycle of oscillation. It is given as a fraction of the cycle or as an angle, where one whole cycle is 2π or 360°], together with a statement of which point is ahead in the cycle.

Question 7

Coherence

Answer 7

Waves or wave sources, which have a constant phase difference between them (and therefore must have the same frequency) are said to be coherent.

Question 8

Stationary (or standing) wave

Answer 8

A stationary wave is a pattern of disturbances in a medium, in which energy is not propagated. The amplitude of particle oscillations is zero at equally-spaced nodes, rising to maxima at antinodes, midway between the nodes.