Waves

Question 1

Displacement (m)

Answer 1

The distance any part of the wave has moved from its mean (rest) position. It can be negative or positive.

Question 2

Amplitude (m)

Answer 2

The maximum displacement, it is always positive.

Question 3

Wavelength

Answer 3

The distance the wave travels before repeating itself.

Question 4

Period

Answer 4

The time to complete one oscillation.

Question 5

Phase difference

Answer 5

The difference, in radians, between two points that have the same pattern of oscillation.

Question 6

Frequency (Hz)

Answer 6

The number of oscillations per unit time at any point, the reciprocal of Period.

Question 7

Speed of a Wave (ms-1)

Answer 7

The waves distance over time. For one Period that would be one wavelength.

Question 8

Stationary or Standing Wave

Answer 8

The wave is not progressive, its peaks and troughs are not moving forward but oscillating in place, so no net transfer of energy. Forms a pattern of Nodes & Antinodes.

Question 9

Nodes (N for “not moving” or “no displacement)

Answer 9

Points in a stationary wave at which there is no displacement at any time.

Question 10

Antinodes (A for maximum Amplitude)

Answer 10

Points in a stationary wave where the displacement varies by the maximum amount.

Question 11

Reflection

Answer 11

The change in direction of a wave at an interface between two different media so that the wave returns into the medium from which it originated.

Question 12

Refraction

Answer 12

The change of direction of a wave that occurs when its speed changes due to a change in medium. velocity/wavelength change, frequency does not

Question 13

Total Internal Reflection

Answer 13

When all of the wave is reflected and there is therefore no refraction. It occurs when the angle of incidence > critical angle. Angles ALL measured from Normal to the surface.

Question 14

Critical Angle

Answer 14

The angle of incidence in a denser medium for which the angle of refraction is 90o
sin (C) = 1 / µ where µ is the refractive index and C the critical angle.

Question 15

Diffraction

Answer 15

Happens when a wave encounters an object or a slit and deviates from its path. The effect is more pronounced for wavelengths roughly comparable to the dimensions of the object or slit.

Question 16

Interference

Answer 16

Occurs when two or more waves overlap and superpose to form a resultant wave where the waves reinforce each other in places and cancel each other in others.

Question 17

Fundamental mode of vibration

Answer 17

The simplest stationary wave where the length is half the wavelength of the wave.

Question 18

Harmonics

Answer 18

A simple multiple of the fundamental frequency.

Question 19

Wavefront

Answer 19

The point on a ripple of a wave that is at the same phase.

Question 20

Coherance

Answer 20

Coherent= constant phase difference (0 or other) between waves.

Question 21

Path difference

Answer 21

The distance from the slit to the point where the waves interfere.

Question 22

Superposition

Answer 22

When two or more waves meet, the total displacement at any point is the sum of the displacements that each individual wave would cause at that point. Note displacement is a vector so direction is important.

Question 23

(Plane) Polarised Wave (applies only to Transverse waves)

Answer 23

Oscillations occur in only one plane or direction, and (as transverse) perpendicular to the direction of travel or propagation.

Question 24

Unpolarised Wave (applies only to Transverse waves)

Answer 24

Oscillations occur in many planes or directions, and (as transverse) perpendicular to the direction of travel or propagation.

Question 25

Longitudinal Wave

Answer 25

Oscillation displacement is parallel to direction of wave or energy travel.

Question 26

Transverse Wave

Answer 26

Oscillation displacement is perpendicular (90o) to direction of wave or energy travel.