waves Flashcards

1
Q

what is amplitude

A

maximum displacement from rest position. larger the amplitude the more energy a wave carries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is wavelength

A

distance between two equivalent points on adjacent waves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is frequency

A

number of waves passing a point each second

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is period

A

the time needed for once complete cycle of vibration to pass a given point

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the correlation between frequency and period

A

as the frequency of a wave increases the period of a wave decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

equation for period

A

period t (seconds) = 1 divided by frequency (Hz)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

wave speed equation

A

wave speed = frequency x wavelength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are electromagnetic waves

A

electromagnetic waves are transverse waves that transfer energy from the source of the waves to an absorber

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

properties of electromagnetic waves

A
reflect
refract 
diffract 
absorb 
transmit
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

how do electromagnetic waves differ from other waves

A

because they can travel through a vacuum

they form a continuous spectrum and all types of electromagnetic wave travel at the same velocity through a vacuum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are waves in electromagnetic spectrum grouped in

A

grouped in terms of frequency and wavelength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

from long to short wavelength or low to high frequency the order of electromagnetic spectrum is

A
radio waves
microwaves
infrared 
visible light 
ultraviolet 
xrays 
gamma rays
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

radio waves in communication long and short

A

transfer energy: short radio wave (10m-100m) can be sent over long distances but have to be reflected of the earths atmosphere (ionosphere)

long radio waves (1-10km) waves can diffract (bend) around earths surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how are radio waves produced

A

radio waves are made by oscillating electric and magnetic fields

AC current creates the oscillating electric and magnetic fields which creates radio waves in a transmitter

receiver absorbs radio waves and the energy is transferred to the elections in material of receiver

the energy absorbed causes the electrons to oscillate and generates an alternating current

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

microwaves used by satellites

A

microwaves are used as they can pass through the earths watery atmosphere

transmitter sends information into space to a satellite

the satellite transmits signal back to earth in a different direction

received by a satellite dish

time delay between signal being sent and received

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

microwaves in microwave ovens

A

microwaves in a microwave oven hv a different wavelength compared to communication microwave

therefore microwaves are absorbed by water molecules in food

microwaves penetrate a few cm into the food before being absorbed and transferring the energy to the water molecules

the water molecules transfer the energy to rest of the molecules in the food

causes the food to heat up

17
Q

required practical : measuring infrared radiation

A
  1. place an empty leslie cube on heatproof mat
  2. boil water in a kettle and fill cube w boiling water
  3. wair a while for the cube to warm up then hold a thermometer against each of 4 vertical faces of the cube. all 4 faces should be same temp
  4. hold an infrared detector a set distance away from one of cubes vertical faces and record the amount of IR radiation it’s detects
  5. repeat the measurement for each of cubes vertical faces. make sure you position the detector at the same distance from the cube each time
  6. you should find that you detect more infrared reaction from the black surface than the white one and more from matt surfaces than shiny ones
  7. as always you should do the experiment more than once to make sure results are repeatable
  8. be careful when doing experiment - don’t move cube when it’s full of boiling water you nufnt burn your hands
18
Q

dangers of EM waves

A

UV radiation damages surface cells leads to sunburn and causes skin to age prematurely

serious effects - blindness and increase risk of skin cancer

x rays and gamma rays are ionizing radiation (ability to knock electrons of their atoms)

cause gene mutations , cell destruction and cancer

radiographers have to wear lead apropos to reduce risk of x ray wxposure

19
Q

what do waves do

A

transfer energy from one place to another

20
Q

what are longitudinal waves

A

particles move side to side - oscillations are parallel to the direction of energy transfer. they show areas of compression and rare fraction sound waves travelling theougj air are longitudinal

21
Q

what are transverse waves

A

oscillations are perpendicular (90 degrees) to the direction of the energy transfer

22
Q

investigating waves required practical

A
  1. pour water to a depth of 5mm into tank
  2. adjust height of wooden rod so that it touches the surface of the water
  3. switch on overhead lamp and electric motor
  4. adjust speed of moter as low frequency waves need to be produced
  5. adjust height of lamp so pattern can be clearly seen on card on floor
  6. place a meter ruler at right angles to the wave shown in pattern on the card. measure across as many waves as possible then divide length by number of waves to give wavelength of waves
  7. count number of waves passing a point in latter on 10s then divide number of waves by 10 to give frenquchcy
  8. calculate speed of waves using equation wave speed = frequency x wavelength
23
Q

what type of waves are sound waves

A

longitudinal

24
Q

what kind of waves are water waves

A

transverse

25
Q

what do longitudinal waves show areas of

A

compression and rare fraction

26
Q

what emits more IR radiating and what absorbs more

A

hotter objects than surrounding EMITS more IR radiotion (cools down )

objects cooler than surrounding ABSORB more IR radiation and warm up

27
Q

what surfaces are btr at emitting radiation

A

black and matt surfaces are btr at emitting & absorbing radiation compared to white to give maximum rate of energy transfer

28
Q

refraction of waves

A

when a wave crosses a boundary between two materials it changes velocity. if the wave is travelling at an angle it changes direction - it is refracted

29
Q

what is optical density

A

optical density of a material is the measure of how quickly light can travel though it. the higher the optical density the slower the light wave travels