Waves

Question 1

Define wave

Answer 1

Vibrations that transfer energy.

Question 2

What are transverse waves?

Answer 2

Waves where wave motion vibrates perpendicular to the direction of energy transfer.

Question 3

What are the properties of transverse waves?

Answer 3

-Energy transfer and wave motion are perpendicular
-Transfer energy, not particles
-Move in solids and on surfaces of liquids (only some in liquids, gases and vacuums
-Constant velocity+ density

Question 4

What are examples of transverse waves?

Answer 4

light, S-waves (seismic), EM waves

Question 5

What are longitudinal waves?

Answer 5

Waves where wave motion vibrates parallel to energy transfer

Question 6

What are the properties of longitudinal waves?

Answer 6

-Energy transfer and wave motion are parallel
-Transfers energy, not particles
- Can move in liquids, solids and gases (not vacuums)
- Changing density+ pressure

Question 7

What is it called when particles are close together in longitudinal waves?

Answer 7

Compression

Question 8

What is it called when particles are far apart in longitudinal waves?

Answer 8

Rarefaction

Question 9

What are examples of longitudinal waves?

Answer 9

Sound waves, P-waves and pressure waves

Question 10

What does a wave front diagram show?

Answer 10

Waves viewed from above

Question 11

What is amplitude?

Answer 11

Distance from undisturbed position to the peak or trough (metres)

Question 12

What is wavelength?

Answer 12

Distance from one point on a wave to the same point on the next wave

Question 13

What is frequency?

Answer 13

The no. of waves passing a point per second (hertz)

Question 14

What is a time period?

Answer 14

Time taken for a single wave to pass a point

Question 15

What is wavespeed?

Answer 15

The distance travelled by a wave each second

Question 16

What is the formula for wavespeed?

Answer 16

Wavespeed= Frequency x wavelength

Question 17

How do we find the speed of sound using two wooden blocks?

Answer 17

Person 1 stands (holding wooden blocks) 100m away from Person 2. Person 2 starts a stopwatch when they see P1 about to hit the blocks-when P2 hears the noise they stop the stopwatch. Repeat this in time with the waves. Calc mean time.
S= D/t

Question 18

How do we find the wave speed using two wooden blocks and a wall?

Answer 18

P1 stands 50m away from a wall next to P2 (holding a stopwatch). P1 claps the blocks and continues to clap in rhythm with the echoes. P2 times between claps- repeat+ find avg. S= (distance to wall)x2 / avg time between claps

Question 19

How do we find wave speed using an oscilloscope?

Answer 19

Two microphones are 5 metres apart and attached to an oscilloscope (shows time taken). A sound is made and the oscilloscope shows the time taken for sound waves to reach microphones.

Question 20

What does an oscilloscope show?

Answer 20

Shows waves on a screen and can tell us time taken for a wave to reach microphones.

Question 21

How do we find wave speed in water?

Answer 21

Apparatus: Ripple tank with paper underneath + light shining on top. To find wavelength, take pic+ place ruler to measure. To find freq, record and count how may wave pass in 10 secs then divide by 10. Speed= wavelength x freq. Or select wave and record to see how long it takes to cover distance of ripple tank.

Question 22

How do we measure wave speed in solids?

Answer 22

Set up apparatus, adjust the frequency of the signal generator until a “solid” wave is produced, once the “solid” wave is produced, record the frequency shown on the signal generator, use a ruler to measure wavelength, the length to measure will depend on the number of “solid” waves produced. Or measure the length of multiple wavelengths, and divide by the number of wavelengths seen, repeat+ adjust the frequency until another “solid” wave is produced

Question 23

What is an electromagnetic wave?

Answer 23

Transverse waves that transfer energy from the source of waves to an absorber

Question 24

What are the properties of EM waves?

Answer 24

Transverse, all travel at same speed in vacuums

Question 25

What properties is the EM wave spectrum arranged in?

Answer 25

Wavelength (H-L) Frequency (L-H)

Question 26

What are the EM waves?

Answer 26

Radio, Micro, Infrared, Visible light, UV, X_rays, Gamma

Question 27

What does a higher frequency mean in waves?

Answer 27

Higher energy, which means highly ionizing so harmful to cells, causing mutations/cancer.

Question 28

What is visible light?

Answer 28

Range of waves visible to the human eye. Red (Lowest freq) , Orange, Yellow, Green, Blue, Indigo, Violet (Highest freq)

Question 29

What is EM radiation?

Answer 29

An energy transfer pathway

Question 30

What do shorter wavelengths mean?

Answer 30

Higher frequency= higher energy, more ionising and harmful. (UV, X-rays, Gamma)

Question 31

Explain energy transfer by microwave ovens.

Answer 31

Water molecules can absorb some wavelengths of microwaves, so energy is transferred by radiation to the thermal energy of the food.

Question 32

Explain energy transfer by infrared waves.

Answer 32

All hot objects emit infrared radiation, these waves can be absorbed by other objects (heating them)

Question 33

Explain energy transfers from the sun.

Answer 33

The sun emits: UV (burns/tans), Infrared (heats), and visible light (allows us to see). All transferred by radiations.

Question 34

What can happen when EM waves move from one medium to another?

Answer 34

They may be: Transmitted, Absorbed, Reflected or refracted.

Question 35

Why do different materials react differently with different EM waves?

Answer 35

The different wavelengths and densities of the materials.

Question 36

Define refraction.

Answer 36

The bending of waves due to switching mediums, so the wave travels at a different speed.

Question 37

What causes refraction?

Answer 37

When a wave enters a different medium, the different parts of the wave enter at different times, leading to a change in speed- causes wave to bend.

Question 38

When a wave moves from a more dense to a less dense, does it move closer or away from the normal?

Answer 38

Away from the normal- speeds up.

Question 39

When a wave moves from a less dense to a more dense, does it move closer or away from the normal?

Answer 39

Towards the normal- slows down.

Question 40

RP10: How do we investigate the amount of infrared radiation absorbed by different coloured surfaces?

Answer 40

Method: Set up identical flasks (diff colors: matt black, shiny black, grey, silver) fill them with hot water and measure start temp. Then start stopwatch +measure temps at regular intervals. Greatest heat loss= best emitter. Or use Leslie's cube + infrared detector.

Question 41

What happens when an atom absorbs EM waves?

Answer 41

The electrons gain energy and move to a higher energy level (outer shell)

Question 42

What happens when an atom emits an EM wave?

Answer 42

The electrons have lost energy and move to a lower energy level (inner shell)

Question 43

How can higher energies (gamma rays) be achieved by an atom?

Answer 43

When an EM wave interacts with the nucleus.

Question 44

How are radio waves produced?

Answer 44

By connecting an antenna to a high frequency ac current power source.

Question 45

What happens in the transmitting antenna and receiving antenna when producing radio waves?

Answer 45

Transmitting: The charge from the ac oscillates up and down the antenna, this produces radio waves. Receiving: Metal aerial absorbs these radio waves, creating an ac with the same frequency as transmitted waves.

Question 46

What are the dangers of high energy EM waves?

Answer 46

Frequency is high, so energy is high. This makes them ionising which damages cells, causing mutations and caner.

Question 47

Define radiation dose.

Answer 47

A measure of the risk of harm resulting from exposure of ionsing radiation. (Sieverts)

Question 48

What are the dangers of radio waves?

Answer 48

No known danger.

Question 49

What are the dangers of infrared waves?

Answer 49

Skin burns

Question 50

What are the dangers of visible light?

Answer 50

bright lights causing eye damage

Question 51

What are the dangers of microwaves?

Answer 51

certain frequencies can be absorbed by water molecules, human body contains lots of water so possible heat damage to internal organs.W

Question 52

Why are microwave ovens considered to be safe?

Answer 52

Although they emit large amounts of microwaves, the glass door and metal walls prevent them from escaping.

Question 53

What are the dangers of UV waves?

Answer 53

High energy= ionising so they can kill skin cells and cause premature aging- skin cancer. Can cause severe eye damage.

Question 54

What are the dangers of X-rays and gamma rays?

Answer 54

Most ionising and penetrate+ damage cells. Cause mutations and cancer.

Question 55

Where are the uses radio waves?

Answer 55

Communication (radios/TV)

Question 56

What are the uses of micrwaves?

Answer 56

Heat food, remotes, electric heaters and infrared cameras

Question 57

What are the uses of visible light?

Answer 57

Taking photos/videos, fibre optic

Question 58

What are the uses of UV waves?

Answer 58

Tans, security markings, fluorescent bulbs

Question 59

What are the uses of X-rays?

Answer 59

X-ray images in medicine/security.

Question 60

What are the uses of gamma rays?

Answer 60

Sterilize medical equipment + treats cancer.

Question 61

Why are radio waves suitable for long range communication?

Answer 61

Can be reflected from the Earth's atmosphere

Question 62

Why are microwaves suitable for satellite communication?

Answer 62

Can penetrate the Earth's atmosphere

Question 63

Why are infrared waves suitable for fibre optic communication?

Answer 63

Can undergo total internal reflection

Question 64

Why is visible light suitable for taking photos/videos?

Answer 64

Cameras are set up to detect visible light.

Question 65

Why are UV rays suitable for detecting security ink?

Answer 65

Ink fluoresces with UV light.

Question 66

Why are X-rays suitable for showing images of bones?

Answer 66

They can penetrate through soft tissues but not bones.

Question 67

Why are gamma rays suitable for sterilising medical equipment?

Answer 67

They kill bacteria