Unit 4 - Waves

Question 1

Write the definition of: Progressive Wave

Answer 1

Transfer of energy as the result of oscillations of the medium through which the energy is travelling

Question 2

Write the definition of: Longitudinal Wave

Answer 2

The oscillation of particles is parallel to the direction of travel of the wave e.g. sound

Question 3

Write the definition of: Transverse Wave

Answer 3

The oscillation of particles is perpendicular to the direction of travel of the wave e.g. waves on a string, electromagnetic

Question 4

Write the definition of: Mechanical Waves

Answer 4

Energy is transferred through a medium (i.e. by the oscillations of particles)

Question 5

Write the definition of: Amplitude

Answer 5

The maximum displacement from the equilibrium position

Question 6

Write the definition of: Wavelength

Answer 6

The minimum distance between two points oscillating in phase, for example the distance between one peak to the next. The length of one complete wave cycle, in metres.

Question 7

Write the definition of: Period

Answer 7

The time taken for one complete wavelength to pass a given point OR the time taken to complete one oscillation. Measured in seconds.

Question 8

Write the definition of: Frequency

Answer 8

Write the definition of: Frequency

Question 9

Write the definition of: Phase

Answer 9

The position of an oscillating particle or field at a given time on a wave cycle, expressed in degrees or radians, where 1 full wave cycle = 360 degrees or 2π radians.

Question 10

how the intensity is related to the amplitude of a wave

Answer 10

intensity is proportional to amplitude squared

Question 11

give the equation for intensity

Answer 11

power/area = intensity

Question 12

Write the definition of: Intensity

Answer 12

The radiant power transferred per unit area (intensity = power / area). Measured in W m-2. Intensity is proportional to amplitude2

Question 13

Write the definition of: Stationary Wave (Standing Wave)

Answer 13

A stationary wave is resultant of the superposition of two progressive waves of the same frequency, moving in opposite directions. The wave remains in a constant position and there is no net transfer of energy. The wave is characterised by its nodes and antinodes.

Question 14

Write the definition of: Antinode

Answer 14

Point of maximum amplitude on a stationary wave

Question 15

Write the definition of: node

Answer 15

Point of minimum amplitude on a stationary wave

Question 16

Write the definition of: Fundamental Frequency

Answer 16

The lowest possible frequency at which a system can vibrate to create a standing/stationary wave

Question 17

Write the definition of: Harmonic

Answer 17

A whole number multiple of the fundamental frequency

Question 18

what is the difference between path and phase difference

Answer 18

they measure the same thing, but path difference measures it in terms of wavelength while phase difference is in radians and degrees

Question 19

how can you find the frequency from an osciloscope trace

Answer 19

calculate the period by multiplying the t/div setting by the number of boxes equal to one wavelength. this gives you the period. then calculate the reciprocal of that value to get the frequency

Question 20

how can you find the amplitude form an oscilloscope trace

Answer 20

the V/div setting times by the maximum number of boxes that one peak reaches

Question 21

how can EM waves be produced

Answer 21

from varying electric and magentic fields

Question 22

what is antiphase

Answer 22

when 2 points have a phase/path difference of pi, 190 degrees, or half a wavelength. when one is at a peak, the other is at a trough

Question 23

give some wave properties

Answer 23

refract, reflect, diffract, diffuse

Question 24

define a polarised wave

Answer 24

a transverse wave which only travels in one plane

Question 25

how does polarisation work

Answer 25

a polariser is a matrerial which only lets waves through in one plane. these polarised waves can then only get through materials with the same polarisation or none at all

Question 26

a polarising material in front of another is turned around 360 degrees, what observations could be seen

Answer 26

every 90 degrees the light intensity would reach a minimum or maximum in alternating order

Question 27

a horizontal polariser is placed in front of a horizontal polariser, what will happen to the image through them and why

Answer 27

there will be no change because they both let through waves in the same direction. the image will remain at maximum intensity

Question 28

a vertical polariser is placed in front of a horizontal polariser, what will happen to the image through them and why

Answer 28

the vertical poalriser polarises waves in the veritcal direction, so that there are non in the horixontal direction meaning that no waves will get through the horizontal polariser and the image will appear black

Question 29

give two applications of polarisers and the reason for their use

Answer 29

in sunglasses because they do not allow some polarised llight through them, decreasing the light intensity that gets through to the eye

Question 30

give the definition of destructive superposition

Answer 30

when 2 waves have aphase difference of 180 degrees, they superpose and the peaks cancel out thr trough

Question 31

give the definition of constructive superposition

Answer 31

when 2 waves have a phase difference of 0 degrees and they superpose to form a waves that has the peaks and troughs as the sum of the previous waves' peaks and troughs

Question 32

give the deifniition of superposition

Answer 32

the process by which two propgressive waves travelling in opposite directions combin into a single wave form when they overlap

Question 33

give the principle of superposition

Answer 33

the resultant displacement of waves is equal to the sum of individual displacements of the waves that are meeting

Question 34

how do nodes and antinodes form

Answer 34

nodes form when destructive superposition occurs between 2 waves and antinodes when constructive super position occurs

Question 35

define a stationary wave

Answer 35

a waveform that is the sum of 2 progressive waves of opposite direction, and same amplitude and frequency

Question 36

why do even numbered harmonics not exist for a pipe with one closed and one open ened

Answer 36

because by definition this type of pipe must have one node at one end and one antinode at the other, therefore its not possible for an even frequency to exist

Question 37

what determines the number harmonic

Answer 37

the multiple of the fundamental fequency

Question 38

in pipes, where do nodes and antinodes form

Answer 38

nodes form at closed ends, and antinodes form at open ends

Question 39

what are coherent waves

Answer 39

waves with a constant phase difference

Question 40

what is intensity

Answer 40

power over area if you take the light emitted by a source to be a sphere, the intensity is the power per area a certain distance from the source.

Question 41

what is the relationship between intensity and amplitude

Answer 41

I ∝ A²

Question 42

define diffraction

Answer 42

The spreading of a wave after passing through a gap or around an obstacle