module 4.4 waves mock revision

Question 1

Progressive Wave

Answer 1

A series of vibrations that transfers energy from one place to another.

Question 2

Longitudinal Wave

Answer 2

A wave where particle oscillations are in the direction of wave propagation. E.g. Sound Waves

Question 3

Transverse Wave

Answer 3

A wave where particle oscillations are perpendicular to the direction of wave propagation

Question 4

Displacement

Answer 4

The distance any part of a wave has moved from its mean or rest position

Question 5

Amplitude

Answer 5

The maximum displacement of a wave from its mean or rest position

Question 6

Wavelength

Answer 6

The smallest distance between two points on a wave that are in phase

Question 7

Period

Answer 7

The time taken for one complete pattern of oscillation

Question 8

Frequency

Answer 8

The number of oscillations at a given point per unit time

Question 9

Speed of a wave

Answer 9

Distance travelled by the wave (energy) per unit time

Question 10

frequency = 1/period

Answer 10

period = 1/frequency

Question 11

𝑆𝑝𝑒𝑒𝑑(𝑣) =𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 (𝑑)/ 𝑇𝑖𝑚𝑒 (𝑡)

Answer 11

→ 𝑆𝑝𝑒𝑒𝑑(𝑣) = 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑀𝑜𝑣𝑒𝑑 (𝜆) /𝑇𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛 (1/𝑓)

v = 𝑓𝜆

Question 12

Reflection

Answer 12

When waves rebound from a barrier, changing direction but remaining in the same medium.

Question 13

Refraction

Answer 13

When waves change direction when they travel from one medium to another due to the difference in wave speed in each medium.

Question 14

Diffraction

Answer 14

When a wave spreads out after passing around an obstacle or through a gap

Question 15

radio waves

Answer 15

used for communication, tv radio

Question 16

microwaves

Answer 16

used in mobile phones, microwave ovens,

communication, heating

Question 17

infrared

Answer 17

heating, remote controls

Question 18

visible light

Answer 18

sight

Question 19

uv

Answer 19

tanning, counterfeit detection

Question 20

x-rays

Answer 20

x-ray photography, security scanners, kill cancer cells

Question 21

gamma rays

Answer 21

cancer treatmet, sterilisation of medical instruments

Question 22

gamma rays

Answer 22

cancer treatment, sterilization of medical instruments

Question 23

the role of sunscreen

Answer 23

Protects the skin from sunburn by absorbing UV-B radiation

UV-B also produces vitamin D

Question 24

All electromagnetic have some properties in common

Answer 24

They all travel at the speed of light in a vacuum and slower speeds in other media

They are transverse waves consisting of vibrating electric and magnetic fields. The electric and magnetic fields are at right angles to each other and the direction of travel.

Like all waves they can be reflected, refracted and diffracted and can undergo interference.

Like all ways they obey v=fλ (v = velocity, f = frequency, λ = wavelength)

Like all progressive waves, progressive EM waves carry energy

Like all transverse waves EM waves can be polarised

Question 25

Some Properties Vary Across the EM Spectrum

Answer 25

The longer the λ the more obvious the wave characteristics Energy is directly proportional to the frequency (E = hf) The higher the energy the more dangerous the wave The lower the energy the further from the nucleus it comes from. - Gamma radiation comes from inside the nucleus. - X-rays to visible light come from energy level transitions in atoms. - Infrared radiation and microwaves are associated with molecules. - Radio waves come from oscillations in electric fields.

Question 26

Plane-Polarised Wave

Answer 26

A transverse wave oscillating in only one plane

Question 27

Polarisation

Answer 27

The process of turning an un-polarised wave into a plane polarised wave.

Question 28

wave phenomena that apply to both longitudinal and transverse waves

Answer 28

diffraction refraction superposition (interference)

Question 29

a wave phenomenon that applies only transverse waves but not longitudinal waves.

Answer 29

Polarisation

Question 30

how polaroid sunglasses can prevent glare from light reflected from a water surface

Answer 30

light reflected from water surface is partially plane polarised alignment of polaroid lens is at right angles to plane of polarisation of reflected light polarised reflected light is not transmitted by polaroid lens

Question 31

Malus's law

Answer 31

A = A0Cosθ so I = I0Cos2θ | I = 1/2I0 after first filter as ½ light goes through.

Question 32

Describe and explain an experiment to demonstrate the polarisation of microwaves

Answer 32

place microwave transmitter and receiver facing each other place two polarising filters (metal grid with bars ~1cm apart) across path of beam observed signal on receiver is maximum intensity when polarising filters are parallel the first filter polarises the beam, the beam can pass through the second filter because the plane of polarisation of the beam matches the alignment of the filter. rotate polarising filter 90^ from parallel to crossed observed signal on receiver drops to minimum intensity (zero) when polarising filters are crossed the beam cannot pass through the second filter when the plane of polarisation of the beam is at 906^ to the alignment of the filter

Question 33

Principle of Superposition

Answer 33

When two or more waves meet at a point the resultant | displacement at that point is the vector sum of the displacements due to each wave.

Question 34

Interference

Answer 34

The vector addition of two or more waves (superposition) that results in a new wave pattern

Question 35

Coherence

Answer 35

Two waves with a constant phase relationship (Same f & λ)

Question 36

Phase Difference (φ)

Answer 36

The angular distance by which one particle leads or lags behind another particle in its pattern of oscillation.

Question 37

Path Difference

Answer 37

The distance between the distances travelled from their sources by two waves meeting at a point.

Question 38

Constructive interference

Answer 38

If two waves exist at the same point and are in phase, the amplitude of the resultant wave will be the sum of the amplitudes of the individual waves

Question 39

Destructive interference

Answer 39

If two waves exist at the same point and are anti-phase, the amplitude of the resultant wave will be zero as the waves cancel each other out.

Question 40

𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 =

Answer 40

𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 = 𝑃𝑜𝑤𝑒𝑟/ 𝐶𝑟𝑜𝑠𝑠 𝑆𝑒𝑐𝑡𝑖𝑜𝑛𝑎𝑙 𝐴𝑟𝑒𝑎 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 ∝ 𝑎𝑚𝑝𝑙𝑖𝑡𝑢𝑑𝑒2

Question 41

n = d sin 0

Answer 41

n is order of maximum [ no units ] λ = wavelength [ m ] d is spacing between slits [ m ] 0 is angle at which maximum occurs [ degrees ]

Question 42

Node

Answer 42

A point that always has zero amplitude along a stationary wave, caused by destructive interference

Question 43

Antinode

Answer 43

A point of maximum amplitude along a stationary wave, caused by constructive interference

Question 44

Fundamental Mode of Vibration (Frequency)

Answer 44

The lowest frequency in a harmonic series where a stationary wave forms.

Question 45

Harmonics

Answer 45

Stationary waves for a particular system with higher frequencies than the fundamental.

Question 46

how a stationary wave is formed

Answer 46

wave travels to end and is reflected reflected wave superposes with incident wave to produce a resultant wave at certain points always destructive interference to produce nodes at certain points always constructive interference to produce antinodes

Question 47

phase difference

Answer 47

how far ‘out of step’ the oscillations at two points | on the wave are

Question 48

stationary wave

Answer 48

a wave which traps/stores energy (in pockets) has nodes and antinodes

Question 49

how is a stationary wave formed

Answer 49

the wave is reflected it interferes/superposes with the incident wave to produce a resultant wave with nodes and antinodes/no energy transfer