P12: Wave properties

Question 1

What is the nature of a wave?

Answer 1

It transfers energy but not matter

Question 2

What is a transverse wave?

Answer 2

A wave in which the oscillations are perpendicular to the direction of energy transfer

Question 3

What is a longitudinal wave?

Answer 3

A wave in which the oscillations are parallel to the direction of energy transfer. (particles move from side to side).

Question 4

What are some examples of transverse waves?

Answer 4

Ripples in water

Question 5

What are some examples of longitudinal waves?

Answer 5

Sound waves

Question 6

What is a mechanical wave?

Answer 6

Vibrations that travel through a medium, e.g. sound waves, water waves, seismic waves.

Question 7

What is an electromagnetic wave?

Answer 7

A wave which travels at the speed of light and does not need a medium to travel, e.g. radio waves, micro waves, light waves.

Question 8

What are the features of longitudinal waves?

Answer 8

Regions where particles are close together - compressions
Regions where particles are far apart - rarefactions

Question 9

What are the differences between longitudinal and transverse waves?

Answer 9

Long - require a medium to travel through, oscillation parallel to direction of energy transfer
Trans - can travel through space, oscillation perpendicular to direction of energy transfer

Question 10

What is the amplitude of a wave?

Answer 10

The maximum displacement of a point on a wave, from the undisturbed position (line)
(drawn from rest to peak/ trough)

Question 11

What is the wavelength of a wave?

Answer 11

The distance from a point on one wave to the equivalent point on the adjacent wave.
(drawn from peak to peak/ trough to trough ( transverse) or drawn from one compression to the next compression/ one rarefaction to the next rarefaction (longitudinal))
Represented by lambda (λ)

Question 12

What is the frequency of a wave?

Answer 12

The number of waves passing a point each second (Hz)
1Hz = 1 wave per second

Question 13

What is the formula for frequency?

Answer 13

Frequency = wavelength/ time
Hz no unit s

Question 14

What is the period of a wave?

Answer 14

The time for one wave to pass a point

Question 15

What is the formula for the period of a wave?

Answer 15

Period = 1/frequency
s Hz

Question 16

What is wave speed?

Answer 16

The speed at which a wave moves through a medium/ the speed at which energy is transferred

Question 17

What is the formula for wave speed?

Answer 17

Wave speed = frequency * wavelength
m/s Hz m

Question 18

What are some problems with the sound wave experiment?

Answer 18

Every person has a different reaction time - can be reduced by having a large number of observers with timers, and calculate a mean.
Difficult to press the timer at the correct time since the interval is so short - fixed by increasing the distance between the two people.

Question 19

How can you measure the speed of soundwaves in air?

Answer 19

Two people will stand a set distance apart e.g. 500 meters. One person will make a sound, e.g. with cymbals, and the other person will start a timer as soon as they see the instruments interact. They will then stop timing when they hear the sound of the cymbals clashing. Speed can be calculated by dividing the speed travelled by the time taken.

Question 20

What happens to waves at the boundary between two different materials?

Answer 20

They are either reflected, transmitted or absorbed

Question 21

What determines whether a wave is transmitted, reflected or absorbed?

Answer 21

The material and the wavelength of the wave

Question 22

What is the rule for the angle of incidence?

Answer 22

Angle of incidence = angle of reflection

Question 23

What are sound waves?

Answer 23

Longitudinal waves. They can pass through one medium to another.

Question 24

How can sound waves be heard?

Answer 24

Sound waves are funnelled into the ear, where they hit the ear drum (thin membrane) and cause it and other parts of the ear to vibrate, causing the sensation of sound/

Question 25

What is the frequency of normal human hearing?

Answer 25

20 - 20,000 Hz, frequencies outside of that may not cause the ear drum to vibrate.

Question 26

What happens to waves when they move from one medium to another?

Answer 26

Their speed can change, e.g. sound waves are faster in solids, as particles are closet together in solids, vibrations can pass more easily between them.
Wavespeed also changes, therefore, so does wavelength (direct proportion).
Frequency does not change, since waves would have to be created or destroyed at the boundary, which is impossible

Question 27

How can you view the features of a sound wave?

Answer 27

Connect a microphone to a cathode ray oscilloscope
Problem - oscilloscope represents sound waves as transverse waves, when they are longitudinal

Question 28

How does frequency affect sound?

Answer 28

High frequency = high pitch
Low frequency = low pitch

Question 29

How does amplitude affect sound?

Answer 29

Small amplitude = quiet sound
Large amplitude = loud sound

Question 30

How do sound waves move?

Answer 30

Must have a medium, because they move by vibrating particles. They cannot pass through a vacuum as there are no particles.
They can be reflected as echoes

Question 31

What is ultrasound?

Answer 31

Soundwaves with a frequency higher than the limit of human hearing.

Question 32

What happens to ultrasound waves at the boundary between two different densities?

Answer 32

Partially reflect

Question 33

How can ultrasound be used to determine the distance of internal organs?

Answer 33

Calculate time taken for ultrasound to leave the probe and bounce off the kidney and be detected by probe, distance can be calculated?

Question 34

What can ultrasound scanners be used for?

Answer 34

To produce images of internal organs, which are not surrounded by bone.
Industrial imaging, e.g. to scan pipes, and detect hidden defects or problems with a weld

Question 35

Why is ultrasound safer than x rays?

Answer 35

Ultrasound does not cause mutations, so there is no risk of cancer

Question 36

What is the internal structure of the Earth?

Answer 36

Crust - outermost layer (thin - 50km deep)
Mantle - under crust (…solid?)
Outer core (liquid)
Inner core (solid)

Question 37

How does an earthquake happen?

Answer 37

Due to the sudden movement between the tectonic plate and the Earth’s crust, causing seismic waves, carrying waves away from the Earth.

Question 38

How can scientists determine the Earth’s internal structure?

Answer 38

Seismic waves pass through the Earth, and can be detected by seismometers in different countries. Patterns of these waves give information about the Earth’s interior.

Question 39

What are the 2 types of seismic waves?

Answer 39

P Waves - longitudinal, can pass through solids and liquids, faster than S waves.
S Waves - transverse waves, only travels through solids.

Question 40

What is the pattern of S waves along the interior of the Earth?

Answer 40

Travel in curved paths due to density changes in the Earth. Can be detected over a certain part of the Earth’s surface, but cannot be detected over the other ( S wave shadow zone). This is because they cannot pass through a liquid, and therefore scientists can deduct that the Earth contains a liquid core.