Vibrations

Question 1

What does a progressive wave do?

Answer 1

Carries energy from one place to another without transferring any material.

Question 2

What is a mechanical wave?

Answer 2

A wave that passes through a substance.

Question 3

What are waves caused by?

Answer 3

• Wave is caused by something making particles or fields oscillate at a source.
• These oscillations pass through the medium as the wave travels, carrying energy with it

Question 4

What happens to the particles of a substance when a wave passes through it?

Answer 4

• When waves pass through a substance, the particles of the the substances vibrate in a way which makes the nearby particles vibrate in the same way.

Question 5

What are electromagnetic waves?

Answer 5

• Oscillating electric and magnetic fields that progress through space without the need for a substance.
• The vibrating electric field generates a vibrating magnetic field, which generates a vibrating electric field further away, and so on.

Question 6

How can you tell that waves carry energy?

Answer 6

• Electromagnetic waves cause things to heat up.
• X rays and gamma rays knock electrons out of their orbits, causing ionisation.
• Loud sounds cause large oscillations of air particles, which can make things vibrate.
• Wave power can be used to generate electricity
• Since waves carry energy away, the source of the wave loses energy.

Question 7

What is a cycle?

Answer 7

One complete vibration of the wave

Question 8

What is displacement?

Answer 8

How far a point on the wave has moved from its undisturbed position.

Question 9

What is amplitude?

Answer 9

Maximum magnitude of displacement

Question 10

What is wavelength?

Answer 10

The length of one whole wave cycle, from crest to crest, or trough to trough.

Question 11

What is the period?

Answer 11

Time taken for a whole cycle to complete, or pass a given point.

Question 12

What is the frequency?

Answer 12

The number of cycles per second passing a given point.

Question 13

What is a phase?

Answer 13

Measurement of the position of a certain point along the wave cycle

Question 14

What is the phase difference?

Answer 14

The amount one wave lags behind another.

Question 15

What are phase/phase difference measured in?

Answer 15

• Degrees

* Fractions of a cycle.

Question 16

What is reflection?

Answer 16

When the wave is bounced back when it hits a boundary

Question 17

What is refraction?

Answer 17

• The wave changes direction, as it enters a different medium.
• The change in direction si a result of the wave slowing down or speeding up.

Question 18

What is the formula for frequency?

Answer 18

1 / Period

Question 19

What is the formula for wave speed?

Answer 19

Distance travelled / Time taken

Question 20

What is the formula for the speed of a wave?

Answer 20

Wavelength x Frequency

Question 21

What are longitudinal waves?

Answer 21

Waves in which the direction of vibrations of the particles is parallel to the direction in which the wave travels.

Question 22

What are some examples of longitudinal waves?

Answer 22

• Sound waves.

* Seismic Waves

Question 23

What does a longitudinal waves consist of?

Answer 23

• Compression and rare fractions of the medium it is travelling through.
• For this fact, they also cannot travel through space without a medium.

Question 24

What are transverse waves?

Answer 24

Waves in which the direction of vibration is perpendicular to the direction in which the wave travels.

Question 25

What are some examples of transverse waves/

Answer 25

• Electromagnetic waves.

Question 26

What does it mean for a wave to be plane pol;polarised?

Answer 26

Waves can be plane polarised if the vibrations stay in one plane only.

Question 27

What does it mean if the vibrations are un-polarised?

Answer 27

They change from one plane to another.

Question 28

What type of waves can be polarised?

Answer 28

• Transverse Waves

* Longitudinal waves cannot be plane polarised.

Question 29

What happens if waves pass through Polaroid filters?

Answer 29

When they pass through the polarising filter, they become polarised because only the vibrations parallel to the slit can pass through it.

Question 30

What does it mean when the filters are crossed?

Answer 30

Two Polarised Filters
• Polarised light from the first filter cannot pass through the second filter, because the alignment of molecules in the second filter is at 90 degrees to the alignment in the first filter, resulting in minimum intensity.

Question 31

What spectrum is light a part of?

Answer 31

Light is a part of the spectrum of electromagnetic waves.

Question 32

What is the plane of polarisation of an electromagnetic wave?

Answer 32

The plane in which the electric field oscillates.

Question 33

What do Polaroid glasses do?

Answer 33

• Reduce the glare of light reflected by water or glass.

* The reflected light is polarised and the intensity is reduced when it passes through the Polaroid sunglasses.

Question 34

How can waves be polarised?

Answer 34

Using a polarising filter.

Question 35

What happens if you have two polarising filters at right angles to each other?

Answer 35

No light will get through.

Question 36

What happens to TV signals?

Answer 36

• They are polarised by the orientation of the rods on the broadcasting aerial, with the rods on the transmitting aerial.
• If they aren’t aligned the signal strength will be lower.

Question 37

What is the correlation between the frequency of a wave and its wavelength?

Answer 37

The higher the frequency of a wave, the shorter its wavelength.