P12

Question 1

What do waves do?

Answer 1

They transfer energy in the direction that they are travelling

Question 2

What is the amplitude of a wave?

Answer 2

It is the maximum displacment of a point on the wave from it’s undisturbed position

Question 3

What is the wavelength?

Answer 3

The wavelength is the distance between the same point of 2 ajacent waves ( for e.g. between the trough of 1 wave and the trough of the wave next to it )

Question 4

What is the crest and the trough?

Answer 4

The top of the wave ( the top of the amplitude ) and the trough is the bottom part of the wave

Question 5

What is frequency?

Answer 5

Frequency is the number of complete waves passing through a certain point per second. It is measured in hertz Hz. 1Hz is 1 wave per second

Question 6

What are the 2 types of waves?

Answer 6

Longitudinal and transverse waves

Question 7

What is the difference between transverse waves and longitudinal waves? Give examples of the different types of waves

Answer 7

In transverse waves the oscillations (vibrations) are at 90 degrees ( they have sideways vibrations ) to the direction of energy transfer. Most waves are transverse including : all electromagnetic waves, ripples/waves in water

Longitudinal waves have oscillations that are parrallel to the direction of energy transfer so there are compressions and rarefractions . Examples are : sound waves in air, ultrasound

Question 8

What’s the equation for wave speed?

Answer 8

Wave speed is the speed at which energy is being transferred or the speed the wave is moving at.
V ( wave speed m/s ) = f ( frequency Hz ) wavelength in m

Question 9

How to measure the speed of sound with an oscilloscope?

Answer 9

-Set up the oscilloscope so that the detected waves at each microphone are shown as seperate waves.

-Start with both microphones next to the speaker then slowly move one away until the two waves are aligned on the display, but have moved one wavelength apart

-Then measure the distance between the microphones to find the wavelength

-Use the formula to find the speed of the sound waves passing through the air

Question 10

How do you measure the speed of water ripples using a lamp?

Answer 10

-Use a signal generator attached to a dipper of a ripple tank so you can create water waves at a set frequency

-Use a lamp to see the wave crests on a screen below the tank and make sure the waves shadows are the same size as the actual waves

-The distance between each shadow line is equivalent to one wavelength. Measure the distance between shadow lines that are 10 wavelengths apart and then divide that by 10 to find the wavelength average

-Use the formula to calculate the speed of the waves

Question 11

How do you do the wave string practical?

Answer 11

-First get a signal generator and connect it to a vibrator tranducer and then connect the tranducer to a string with a pulley and weight on the end of it so that the string is straight

-Adjust the frequency of the signal generator until there’s a clear wave on the string

-Then measure the wavelength of the waves and measure about 4 halfwavelengths and then divide this to get the mean half wavelength and then double it to get the full wavelength

Question 12

What are the 3 things that could happen when waves arrive at a boundary between 2 different materials?

Answer 12

-The waves are absorbed by the material that the wave was trying to cross into - this transfers energy into the materials energy stores

-The waves are transmitted - the waves carry on travelling through the new material - this often leads to refraction

-The waves are reflected

Question 13

What does the angle of incidence =

Answer 13

Angle of incidence = angle of reflection

Question 14

What is specular reflection?

Answer 14

It is when a wave is reflected in a single direction by a smooth surface e.g. when light gets reflected of a mirror

Question 15

What is diffuse reflection?

Answer 15

It is when a wave is reflected by a rough surface and the reflective rays are scattered in lots of different directions. This happens because the normal is different for each incoming ray, which means that the angle of incident is different for each ray

Question 16

What happens when light is reflected by a rough surface?

Answer 16

The surface appears matte and you don’t get a clear reflection of objects

Question 17

What happens when a wave crosses a boundary between materials at an angle?

Answer 17

It gets refracted

Question 18

How much a wave is refracted depends on how much it ……. or ………

Answer 18

Speeds up or slows down

Question 19

What happens when a wave crosses a boundary and slows down or speeds up?

Answer 19

It will bend towards the normal when it slows down and it will bend away away from the normal if it speeds up.

Question 20

What changes about the wave when it’s refracted?

Answer 20

The wavelength changes when a wave is refracted, but the frequency stays the same

Question 21

If a wave is travelling along the normal it will change speed but not…..

Answer 21

Refract

Question 22

What are sound waves caused by? And what are they?

Answer 22

They are caused by vibrating objects and they are a series of compressions and refractions

Question 23

What happens when a sound wave travels through a solid?

Answer 23

When a sound wave travels through a solid it does so by causing the particles in the solid to vibrate.

Question 24

Explain how your ear hears sound

Answer 24

Sound waves that reach your ear drum can cause it to vibrate.

These vibrations are passed on to tiny bones in your ear called ossicles, through the semi-circular canals and to the cochlea.

The cochlea turns these vibrations into electrical signals which get sent to the brain and allow you to hear sound

Question 25

What are echoes?

Answer 25

They are reflected sound waves

Question 26

What is ultrasound?

Answer 26

Ultrasound is sound with frequencies higher than 20,000Hz

Question 27

What is partial refraction?

Answer 27

It is when a wave passes from one medium to another and some of the wave is reflected and some refracted. This is what happens to ultrasound waves

Question 28

Why is partial reflection good for ultrasound?

Answer 28

What this means is that you can point a pulse of ultrasound at an
object, and wherever there are boundaries between one substance
and another, some of the ultrasound gets reflected back.

Question 29

How is ultrasound work in scanning a foetus?

Answer 29

Ultrasound waves can pass through the body, but whenever they reach
a boundary between two different media (like fluid in the womb and the
skin of the foetus) some of the wave is reflected back and detected.

The exact timing and distribution of these echoes are processed by
a computer to produce a video image of the foetus.

Question 30

How can ultrasound be usefull in finding flaws in materials?

Answer 30

Ultrasound waves entering a material will usually be reflected by the far side of the material.

If there is a flaw such as a crack inside the object, the wave will be reflected sooner.

Question 31

What do earthquakes produce?

Answer 31

Seismic waves

Question 32

What are the 2 types of seismic waves? What are they and what do they do?

Answer 32

P waves - they are longitudinal - they travel through solids and liquids - they travel faster than S-waves

S waves - they are transverse and can’t travel through liquid or gases - they are slower than P-waves

Question 33

What’s the equation for a period?

Answer 33

Period (s) = 1/f (Hz)

Question 34

What are mechanical waves? And give some examples

Answer 34

Mechanical waves are vibrations that travel through a medium ( a substance )
Some examples are: sound waves, water waves, waves on springs and ropes and seismic waves produced by earthquakes