11.2 - Wave Properties

Question 1

What is the definition of displacement?
Symbol
Unit

Answer 1

The distance and direction of a vibrating particle / point in a field from an equilibrium position - a vector
Symbol: s
Unit: m - metres

Question 2

What is the definition of amplitude?

Answer 2

The maximum displacement from a vibrating particle/field from the equilibrium position (height of crest / depth of trough)
Symbol - A
Unit - m (metres)

Question 3

What is the definition of wavelength?
Symbol
Unit

Answer 3

The maximum distance between 2 points on different waves that vibrate with the same velocity at the same displacement IN PHASE

Symbol - lambda
Unit: m (metres)

Question 4

What is the period of oscillation?
Symbol
Unit

Answer 4

The time taken for one oscillation, the time taken for wave to move one whole wavelength past a given point
Symbol T
Unit: s - seconds

Question 5

What is the definition of frequency?

Unit

Answer 5

The number of waves past a given point PER UNIT TIME
number of cycles passing a fixed point every second

Unit: Hz

Question 6

What is wave speed?
Symbol
Unit

Answer 6

Distance travelled by wave per unit time
v ( or c)
m s-1

Question 7

What is the wave equation?

Answer 7

v = f x lambda

Question 8

What is the wave speed like as a wave travels through a medium?
What does this mean as frequency changes?
As a wave crosses between media what happens?

Answer 8

The speed remains constant as it is determined by the properties of the medium
Thus… - the higher the frequency of a given type of wave, the shorter its wavelength

The speed is a fundamental property that changes when crosses between media, which leads to changes in wavelength (but never frequency)

Question 9

Give the equation relating the frequency f of a wave in Hz to its period T in s

Answer 9

f = 1/T

Question 10

What is a wave profile?

Answer 10

A graph showing the displacement of particles in a wave against the distance along the wave

useful way to think about it - ‘a snapshot’ of a wave

Question 11

What is phase difference?

Answer 11

Phase difference describes the difference between the displacements of particles along a wave, or the difference between the displacements of particles on different waves

Question 12

What does a complete cycle or wave represent in degrees and radians?

Answer 12

360 degrees, 2 pi radians

Question 13

What is the phrase ‘in phase’?

Answer 13

If particles are oscillating perfectly in step with each other (they both reach maximum positive displacement at the same time) they are described as being in phase. They have a phase difference of 0.

Question 14

If two particles are separated by a distance of one whole wavelength, what is their phase difference?

Answer 14

360 degrees, or 2 pi radians

Question 15

If two particles are separated by a distance of two whole wavelengths, what is their phase difference?

Answer 15

720 degrees, or 4 π radians

Question 16

What does particles being described as ‘antiphase’ mean?

Answer 16

If particles are oscillating completely out of step with each other (one reaches its maximum positive displacement at the same time as the other reaches its maximum negative displacement) then they’re described as being in antiphase.

Question 17

What is the phase difference of particles in antiphase?

Answer 17

(odd integer) π radians

e.g. 3π radians or 540 degrees

Question 18

What is a radian?

Answer 18

a unit of measurement of angles equal to about 57.3°, equivalent to the angle subtended at the centre of a circle by an arc equal in length to the radius.

Question 19

What is a displacement-time graph?

Answer 19

A graph that can be used to show how the displacement of a given particle of the medium varies with time as the wave passes through the medium. Graph looks the same for both transverse and longitudinal waves.