3.1 Longitudinal & Transverse Waves

Question 1

What is a progressive wave defined as?

Answer 1

A wave that transfers energy from one point to another without transferring the medium itself

Question 2

What are the properties of a progressive wave? (6(

Answer 2

• displacement
• amplitude
• wavelength
• time period
• frequency
• speed

Question 3

What is the displacement of a wave?

Answer 3

• distance of a point on the wave from its equilibrium position

Question 4

What is the Amplitude of a wave?

Answer 4

• the maximum displacement of a particle in the wave from its equilibrium position

Question 5

What is the wavelength of a wave?

Answer 5

• the distance beterrn points on successive oscillations of the wave
• measured in metres

Question 6

What is the time period of a wavE?

Answer 6

• the time taken for one complete oscillation or cycle of the wave
• measured in seconds

Question 7

What is the frequency of a wave?

Answer 7

• the number of complete oscillations per unit time
• measured in Hertz

Question 8

What is the equation for frequency?

Answer 8

frequency = 1/time period

Question 9

What is the speed of a wave?

Answer 9

• the distance travelled by the wave per unit time
• (metres per second)

Question 10

What is the wave equation?

Answer 10

speed of a wave = frequency x wavelength

Question 11

What does the wave equation show?

Answer 11

as the wavelength increases, the frequency decreases and vis a versa

Question 12

What is phase difference?

Answer 12

the phase difference between two waves is a measure of how much a point or wave is in front or behind another

Question 13

how can you find the phase difference?

Answer 13

• the relative position of the crests or troughs of two different waves of the same frequency

Question 14

What determines whether 2 waves are in or out of phase?

Answer 14

• when crests and troughs are aligned in phase
• when crest of one wave aligns with the trough of another they are in anti phase

Question 15

How can the phase difference be calculated?

Answer 15

• from 2 different points on the same wave
• same point on 2 different waves

Question 16

How can phase difference be measured?

Answer 16

• fractions of a wavelength
• degrees
• radians

Question 17

if a wave is in phase, how can it be described?

Answer 17

• 360 degrees
• 2π radians

Question 18

if a wave is in anti-phase, how can it be described?

Answer 18

• 180 degrees
• π radians

Question 19

What are the 2 types of waves?

Answer 19

• transverse
• longitudinal

Question 20

How can you determine what type of wave a wave is?

Answer 20

by the direction of the oscillations in relation to the direction the wave is travelling

Question 21

What is a transverse wave?

Answer 21

a wave in which the particles oscillate perpendicular to the direction of the wave travel and energy transfer

Question 22

What are the properties of transverse waves?

Answer 22

• show areas of crests and troughs
• can be shown on a rope
• can be polarised

Question 23

What are 2 examples of transverse waves?

Answer 23

• electromagnetic waves
• vibrations on a guitar string
• waves on a string
• seismic waves

Question 24

Longitudinal wave is defined as:

Answer 24

a wave in which the particles oscillate parallel to the direction of the wave travel and energy transfer

Question 25

What are some characteristics of longitudinal waves?

Answer 25

• shows areas of compressions and rarefactions
• shown on a link spring
• cannot be polarised

Question 26

How is energy transmitted in a longitudinal wave?

Answer 26

• the medium vibrating as they are given energy
• compressions cause the nearby particles to also vibrate with more energy
• produces a compression further along in the medium

Question 27

What are examples of longitudinal waveS?

Answer 27

• sound waves
• ultrasound waves
• waves through a slinky
• seismic waves

Question 28

What are compressions of a wave?

Answer 28

regions of increased pressureW

Question 29

What are rarefactions of a wave?

Answer 29

regions of decreased pressure

Question 30

What is polarisation?

Answer 30

when particles oscillations occur in only one of the directions perpendicular to the direction of wave propagation

Question 31

Why can polarisation only occur in transverse waves?

Answer 31

because transverse waves oscillate in any plane perpendicular to the propagation direction

Question 32

What does it mean when transverse waves are polarised?

Answer 32

• vibrations are restricted to one direction
• vibrations here are still perpendicular to the direction on propagation/energy transfer

Question 33

Why can longitudinal waves not be polarised?

Answer 33

• they oscillate parallel to the direction of travel

Question 34

How can waves be polarised?

Answer 34

through a
- polariser
- polarising filter

Question 35

How do polarisers work?

Answer 35

they only allow oscillations in a certain plane to be transmitted

Question 36

what are some examples of polarisation?

Answer 36

• sunglasses
• photography
• radio and microwave signals

Question 37

How do polaroid sunglasses work?

Answer 37

• they contain lenses with filter transmission axes that are vertically oriented
• the glasses don’t allow any horizontal polarised light to pass through
• when light is reflected from a surface it undergoes partial polarisation
• thus the glasses reduce the glare on the surface allowing things to be viewed more clearly

Question 38

What is partial polarisation?

Answer 38

if the surface is horizontal, a proportion of the reflected light will oscillate more int he horizontal plane than in the vertical plane

Question 39

How does Polaroid Photography work?

Answer 39

• work in the same way as glasses
• allow photographers to take photos of objects underwater

Question 40

How can polaroid cameras take photos underwater?

Answer 40

• light reflected on the surface of the water is partially polarised in the horizontal plane
• the glare is eliminated by the polarising lens
• light from underwater objects is refracted by the surface of the water thus not plane polarised
• thus the light from the underwater object is more intense than the glare and how’s up much more brightly in the photo

Question 41

How does polarisation of radio and microwave signals occur?

Answer 41

• radio and television services are broadcast either horizontally-polarised or vertically-polarised
• the reception aerial needs to be mounted flat or on its side
• the orientation of the aerial wall depend on the transmitter it is pointing towards and the polarity of the services being broadcast