Topic 3: Waves

Question 1

What do waves do?

Answer 1

transfer energy from one place to another, without transferring any matter

Question 2

What are the different parts of a transverse wave?

Answer 2

Wavelength - distance from one point on one wave to the same point on the adjacent wave
Amplitude - The maximum displacement of a point on a wave away from its undisturbed position.

Question 3

What are the different parts of a longitudinal wave?

Answer 3

Rarefaction - Area of low pressure (particles far apart)
Compression - Area of high pressure (particles close together)

Question 4

What’s a wave period?

Answer 4

Time taken for one complete wave to be produced

Question 5

What’s wave frequency?

Answer 5

The number of waves past a certain point in one second

Question 6

What are some examples of transverse and longitudinal waves?

Answer 6

Transverse - Water ripples, light
Longitudinal - Sound, ultrasound

Question 7

What are the differences between Transverse and Longitudinal waves?

Answer 7

Transverse - Vibrations are perpendicular to the direction the wave travels
Longitudinal - Vibrations are parallel to the direction the wave travels
Transverse - Can travel in vacuums
Longitudinal - Can’t travel in vacuums

Question 8

What’s wave speed?

Answer 8

The speed at which the energy is transferred through a medium
Wave speed = frequency x wave length
OR
Wave speed = distance/time

Question 9

How can you measure the speed of sound in air?

Answer 9

• 2 people stand 500m apart
• Person 1 fires off a gun into the air and holds their arm up simultaneously
• person 2 records how long it takes for them to hear the bang
• Divide the distance by the time it took to hear the sound
• ERRORS: The values will be recorded will be dependent on the reaction time of the observer and so the reaction time won’t be completely accurate

Question 10

What does it mean when waves are transmitted/absorbed?

Answer 10

Transmitted - Wave passes through the material (often leads to refraction)
Absorbed - Wave is taken into the material

Question 11

What’s wave reflection?

Answer 11

Reflection is when a wave bounces off the material at the same angle that it hit

Question 12

What’s wave refraction?

Answer 12

The change in direction of a wave when it travels from one medium to another

Question 13

What happens when light travels into dense/less dense materials?

Answer 13

When light travels into a DENSER material, it SLOWS DOWN and bends TOWARDS the normal

When light travels into a LESS DENSE material, it SPEEDS UP and bends AWAY from the normal

Question 14

What happens when a wave is absorbed into a material?

Answer 14

• the wave transfers energy to the material’s energy stores
• often, it is transmitted to a thermal energy store, which leads to heating (this is how a microwave works)

Question 15

How can we measure the speed of waves in a solid?

Answer 15

• measure the frequency of waves produced when you hit a solid
• Measure and recrd the length of a metal rod e.g. brass
• set up the apparatus so that you have elastic bands held by clamps holding the rod in the centre
• tap the rod with the hammer and write down the peak frequency displayed by the microphone
• repeay 3 times to get an average peak frquency
• Calculate speed of the wave using velocity = frequency x wavelength

Question 16

What’s the material interface?

Answer 16

The boundary between two different materials

Question 17

What is uncertainty?

Answer 17

The interval within which the true value of a quantity can be expected to lie
It is determined by finding the range of data and dividing it by 2

Question 18

Work out the uncertainty for this data set:

25, 50, 14, 22, 31

Answer 18

Range: 50 - 14 = 36
Uncertainty: 36/2 = 18

Question 19

How can you calculate wave frequency?

Answer 19

Frequency = velocity/wavelength

Question 20

Why can’t sound waves travel in space?

Answer 20

Space is mostly a vacuum, sound waves are longitudinal which can’t travel through vacuums

Question 21

What happens when you hear sounds?

Answer 21

• Sound waves reach your ear drum, causing it to vibrate
• These vibrations are passed onto tiny bones in your ear called OSSICLES, through the SEMICIRCULAR CANALS and to the COCHLEA
• The cochlea turns the vibrations into electrical signals which get sent to your BRAIN
• The brain interprets these signals as sounds of different pitches and volumes depending on their frequency and intensity - higher frequency = higher pitch

Question 22

What is human hearing limited by?

Answer 22

The size and shape of our eardrum and the structure of all the part within the ear that vibrate to transmit the sound wave

Question 23

What are the waves on the electromagnetic spectrum?

Answer 23

Raging Martians Invaded Venus Using X-ray Guns

Question 24

What is the trend in the electromagnetic spectrum?

Answer 24

Start - long wavelength, low frequency
End - Short wavelength, high frequency