Waves

Question 1

What are waves?

Answer 1

Repeated vibrations of energy transfer

Question 2

How is energy transferred?

Answer 2

By waves knocking neighbouring particles

Question 3

What is a transverse wave?

Answer 3

Waves where points along the wave vibrate perpendicular to the direction of energy transfer

Question 4

For a transverse wave

Answer 4

The energy transfer is in the same direction as the motion
They transfer energy but not particles of the medium
They move through liquids and solids but not gas
Some can travel through a medium (EM WAVES)

Question 5

Examples of TRANSVERSE waves

Answer 5

• Ripples on the surface of the water
• Vibrations on a guitar string
• S waves
• EM waves

Question 6

What are longitudinal waves?

Answer 6

Waves were the points along the wave vibrate parrallel to the direction of energy transfer

Question 7

Properties of a longitudinal wave

Answer 7

• Energy transfer is in the same direction as motion
• Transfer energy but not particles of a medium
• CAN moves through liquids solids and gas
• They CANT travel through a vacuum as there are no particles

Question 8

Examples of longitudinal waves

Answer 8

• Sound waves
• P waves
• Pressure waves

Question 9

What is amplitude, wave length, wave frequency and time period?

Answer 9

Amplitude= Distance from the undisturbed position of the wave to the peak or trough - METRES
Wavelength= The distance from one point on a wave to the same point on the next wave - METRES (Symbol is lambada)
Wave frequency= The amount of waves that pass a point in one second - HERTZ
Time period= The time take for one wave to pass a point - SECONDS

Question 10

Equation for wave speed

Answer 10

Wave speed = Frequency x Time

Question 11

What do transverse waves have?

Answer 11

Peaks and troughs

Question 12

What do longitudinal waves have?

Answer 12

Rarefactions and compressions

Question 13

How are sounds waves transmitted?

Answer 13

Longitudinal waves work by the molecules vibrating and knocking into vibrating particles/molecules.
The more molecules that are present the more faster the wave can transfer energy

Question 14

In what medium do sound waves travel fastest?

Answer 14

In solids and slowest in gases

Question 15

Refraction of sound

Answer 15

When sound waves travel from a denser medium to a less dense medium their:
Wavelength increases
Frequency stays the same
Velocity increases

Question 16

What is reflection?

Answer 16

When a wave hits a boundry between two media and doesnt pass through

Question 17

Rule for the angles of incidence and reflection?

Answer 17

The angle of incidence=angle of reflection

Question 18

Reflection on flat surfaces

Answer 18

Flat surfaces are much smoother so the stronger the reflected ray

Question 19

Reflection on rough surfaces

Answer 19

Least reflective, because the light scatters in all direction

Question 20

What do opaque surfaces reflect?

Answer 20

Opaque surfaces reflect the light that isnt absorbed by the material
The electrons will absorb the light energy then reemit it as a reflective wave

Question 21

What is transmission?

Answer 21

When a wave passes through a substance

Question 22

What happens when a wave is transmitted through a material?

Answer 22

It is partially absorbed so the transmitted wave has a smaller amplitude

Question 23

What is absorbtion?

Answer 23

When the energy is transferred from the wave to the particles of a substance
Waves can be partially or completely absorbed

Question 24

When will light be absorbed by a material?

Answer 24

When the frequency of the wave matches the levels of the electrons

Question 25

How do sound waves travel through solids

Answer 25

Sound waves are vibrations of air particles When a sound wave comes in contact with a solid, these vibrating air particles are transferred to the solid The compressions and rarefactions cause changes in pressure so sound waves are a type of pressure wave

Question 26

How do sound waves in ears transfer sound?

Answer 26

The sound wave travels down the auditory canal towards the ear drum The pressure of the sound wave exerts a force on the eardrum which causes the ear drum to vibrate The ear drums vibrations are transferred onto 3 small bones which then transfers vibrations into the inner ear The inner ear nerve cells detect the sound and transfer electrical signals to the brain

Question 27

What frequency do humans hear at?

Answer 27

20Hz - 20,000Hz

Question 28

What is ultrasound?

Answer 28

Sound waves with a frequency of greater than 20,000Hz

Question 29

What is infrasound?

Answer 29

Sound waves with a frequency less than 20Hz

Question 30

What may happen to ultrasound when meeting a boundary between two media?

Answer 30

May be partially reflected, transmitted or absorbed

Question 31

When is the greatest percentage of the wave reflected between media?

Answer 31

When the difference in the speeds in the media is large

Question 32

What is echo sounding? What does it use? And what does it show?

Answer 32

Echo sounding is a sound wave which uses ultrasound to detect the depth of the ocean. The time it takes for the wave to return determines the depth

Question 33

How is ultrasound used in medicine?

Answer 33

To construct images of a foetus To generate images of internal organs As a medical treatment to remove kidney stones

Question 34

What is an ultrasound detector made of

Answer 34

A tranduscer which detects and producers a beam of ultrasound

Question 35

How does an ultrasound work

Answer 35

The ultrasound waves are reflected back to the tranduscer by boundries between tissues in the path of the beam When these echoes hit the tranduscers they generate electrical signals that are sent to the ultrasound scanner to build an image

Question 36

Is ultrasound harmful?

Answer 36

No it is believed to be harmless and non-invasive

Question 37

How are ultrasounds used in industry?

Answer 37

A crack in a metal will cause some kind of bump on the oscilliscope as the wave is reflected back earlier than the rest

Question 38

What waves do earthquakes produce?

Answer 38

P-Waves (primary waves) | S-Waves (secondary waves)

Question 39

How are earthquake waves detected?

Answer 39

Using a seisometer

Question 40

P wave properties

Answer 40

``` Longitudinal waves Can pass through solids and liquids Faster than s waves They are low infrasound waves Only refract when pass through different layers of the earth ```

Question 41

S wave properties

Answer 41

Transverse waves Cant move through liquids only solids Slower than P waves

Question 42

What do seismic waves show?

Answer 42

Only P waves are detected on opposite sides of the earth so the mantle is solid as both waves can pass through it but the outercore is liquid The inner core is solid due to the size and positions of the shadow zones created by p waves.