Waves

Question 1

What is a progressive?

Answer 1

A progressive wave transfers energy without transferring material and is made up of particles of a medium oscillating.

Question 2

Define frequency

Answer 2

Number of completed oscillations passing through a point per second

Question 3

Define wavelength

Answer 3

The length of one whole oscillation

Question 4

Define Phase

Answer 4

A position of a certain point on a wave cycle

Question 5

Define Phase difference?

Answer 5

How much a particle lags behind another particle/wave

Question 6

Define Period

Answer 6

Time taken to complete one full oscillation

Question 7

State characteristics of two points that are in phase

Answer 7

• they’re at the same point of a wave cycle
• same displacement and velocity
• phase difference of a multiple of 2pi
• same frequency and same wavelength
• do not need the same amplitude

Question 8

In terms of half cycles how do you determine if two waves are out of phase?

Answer 8

If they’re at odd integers of half cycles apart e.g 5 half cycles (one half cycle is pi)

Question 9

Formula for wave speed (c)

Answer 9

speed = frequency * wavelength (c = f * lander)

Question 10

Define transverse wave and give examples:

Answer 10

An oscillation of particles perpendicular to direction of energy transfer e.g all electromagnetic waves (radio waves, microwaves, light waves) , ripples in water, guitar strings etc

Question 11

Define longitudinal waves and give examples:

Answer 11

• An oscillation of particles parallel to direction of energy transfer
• Made up of compressions and rarefractions that can’t travel in vacuums
  e.g sound waves

Question 12

What can transverse waves only do and what is its functions?

Answer 12

Can be polarised into one plane, which gives evidence to its perpendicular nature
- used in sunglasses to reduce glare or in TV signals where its strength is determined by the orientation of the rods.

Question 13

What is superposition? and give me the two types.

Answer 13

When the displacements of two waves combine with each other as they pass:
Constructive interference - when 2 waves have displacement in the same direction
Destructive interference - when opposite displacements but equal in magnitude combine

Question 14

How is a stationary wave formed?

Answer 14

From the superposition of two progressive waves, travelling in opposite directions in the same plane with the same frequency, wavelength and amplitude.
No energy is transferred in the stationary wave.

Question 15

In a stationary wave what happens to points in the waves that meet completely out of phase and in phase?

Answer 15

• in phase, constructive interference occurs where antipodes are formed at maximum amplitudes.
• Completely out of phase, destructive interference occurs where nodes are formed at equilibrium.

Question 16

Give an example of stationary waves?

Answer 16

Guitar strings and microwaves.

• a string fixed to one end where the wave travelling down due to the oscillator is reflected at the fixed end causing two progressive waves of the same wavelength, frequency and amplitude causing superposition so a stationary wave is formed.

Question 17

What is the first harmonic and how can frequency be calculated?

Answer 17

It is the lowest frequency at which a stationary wave is formed, with two nodes and one antinode. The distance between adjacent nodes is half a wavelength.

f = 1/2L * Square root T/mass per unit length (in formula sheet)

Question 18

Describe how stationary microwaves are formed

Answer 18

formed by reflecting microwave beams at a metal plate

you find nodes and antinodes using a microwave probe

Question 19

Describe stationary sound waves:in a glass tube with sand

Answer 19

formed by placing speakers at one end of a closed glass tube where power lays across the tube.
It will be shaken at antinodes and settle at nodes.

Question 20

How does increasing the wavelength change the pattern produced on the screen in diffraction?

Answer 20

• the central maxima would become wider
• the distance between central maxima and consecutive maxima become greater

Question 21

how do convert 500 lines per mm into what you need for d

Answer 21

(1/500) *10^-3

DO NOT DO: (1/500*10^-3)

Question 22

How do you work out max acceleration of a wave

Answer 22

• Use the max acceleration formula on the simple harmonic section

Question 23

How does a pattern prove an electron has wave properties

Answer 23

• Diffraction and interference
• waves superpose to form bright and dark fringes when in phase
• Slit causes waves to spread out

Question 24

How does a fluorescent screen show that electrons behave as particles

Answer 24

• electrons provide enough kinetic energy for instant excitation
• light emission due to excitation and de-excitation
• collision between incident electrons and moving electrons

Question 25

How would the diffraction pattern of white light differ from red laser light

Answer 25

= central white bring - all subsidiary maxima are of the spectrum - less spaced out fringe

Question 26

What has higher index core or cladding

Answer 26

core

Question 27

If blue light has a greater refractive index which is faster blue or red light

Answer 27

Red light

Question 28

What type of problem occurs due to red and blue light in a core

Answer 28

Red reaches before blue causing material pulse broadening

Question 29

What is a progressive wave?`

Answer 29

When waves transfer energy from one point to another without transferring material

Question 30

Can sound waves interfere

Answer 30

Yes, all waves must be able to diffract and interfere