3 Waves, Sound and EM Spectrum Flashcards
An ambulance is producing sound represented by wave 2
Which wave would represent the sound an observer would hear as the ambulance approached them?
Wave 3.
frequency increases and wavelength decreases as the ambulance approaches the observer.
What is the use of UV radiation?
flourescent lamps
used to detect conterfeit money
Give three properties (features) common to all EM waves
all travel at the same speed in a vaccum (3 x 108m/s)
all transverse waves
all travel through a vacuum
Which wave has the largest wavelength?
wave 1
largest distance between adjacent crests
How can you make a transverse wave with a slinky?
Move your hand in a side to side movement
Equation:
Wave speed v =
wave speed = wavelength x frequency
Label the compressions, rarefactions and wavelength on the longitudinal wave below
What is 204 nm in m?
n stands for nano (x10-9)
204 x 10-9 m
What is the Doppler effect?
When there is a change in frequency of a wave if the source is moving towards or away from an observer.
How can you make a longitudinal wave with a slinky?
move your hand in a forwards and backwards movement
An ambulance is producing sound represented by wave 2
Which wave would represent the sound an observer would hear as the ambulance travelled away from them?
Wave 1.
The frequency of the sound would decrease and wavelength increase as the ambulance moves away from the observer.
Fred noticed that 10 waves passed a point in 5 seconds. What is the frequency of the wave?
frequency = 10 waves/ 5 s
= 2 Hz
What is 700 µm (micrometres) in metres?
µ = x 10-6
700µm = 700 x 10-6 m
What is a wavefront?
A wavefront connects all points on a wave which are moving in time
Which wave has the largest amplitude?
wave 2
It has the largest displacement from the equilibrium
What is the unit for time period?
seconds or s
What is the unit for amplitude?
metres (m)
Match the following terms with their definition
frequency- the number of waves going past in one second
wavelength- the length of one repeat of the wave pattern
wave speed- how far a wave travels in one second
Why are UV waves dangerous?
cause blindness
damage surface skin cells and cause skin cancer
What is the use of microwaves?
cook food
mobile phones
satellites to send signals to satellite dishes
What is a transverse wave?
Where the oscillation is 90° to the direction of wave travel
What are the uses of infrared radiation (IR)
heaters
night vision
emitted by tv controllers to control t.v.
What is the use of X-rays?
Used to detect breaks in bones
look inside materials for breaks eg wings of planes
List the EM spectrum in order of increasing frequency
Radio
Microwave
IR
Visible
UV
X-ray
Gamma
What is 13 kHz in Hz?
kilo k = x 103
13kHz = 13 x 103 Hz
What is the relationship between time period and frequency?
frequency = 1 / time period
List the EM spectrum in order of decreasing wavelength
Radio
Microwave
IR
Visible
UV
X-ray
Gamma
How is gamma radiation dangerous?
It can cause mutations in cells- cancer
How are X-rays dangerous?
They can cause mutations of cells- cancer
Label the wavelength, amplitude, crest and trough of the transverse wave below
How is infrared dangerous?
It can cause skin burns if too hot
What is a longitudinal wave?
oscillations are parallel to the direction of travel.
Give three examples of a longitudinal wave
sound
shock wave
P wave
What are the uses of radio waves?
broadcasting radio and tv signals
radar
walkie talkie signals
What are the uses of gamma radiation?
Used to kill cancer tumours
used to sterilise medical equipment and food
What is 100 MHz in Hz?
mega M = x 106
100MHz = 100 x 106 Hz
What is the unit for wavelength?
metre or m
Give three examples of a transverse wave
water wave
any EM wave
S wave
Which wave has the highest frequency?
wave 3
it has more waves per second
How are all the EM radiation different?
They have….
different wavelengths
different frequencies
therefore they have different uses and dangers
What is the unit for wavespeed?
metre per second or m/s
What is the use of visible light?
photography
fibre optics
What is the unit for frequency?
Hertz or Hz
How is sound created?
sound is created by vibrations
List some properties of sound
- it is a longitudinal wave
- it is created by a vibration
- it cannot travel through a vacuum
Does increasing temperature increase the speed of sound in air?
Why?
No
As temperature of air increases, speed of sound decreases.
Particles in warm air are more spread out and collisions between particles are more difficult
Sound is a series of compressions and rarefactions.
How does the speed of sound compare in a solid, liquid and gas? Explain
Sound travel faster through a solid than a liquid and gas.
Sound is a vibration which is transferred from particle to particle via collisions.
Solid particles are closer together and have stronger forces between them- vibrations are passes between particles more quickly
How can speed of sound through air be measured in a laboratory?
- connect two microphones to a microsecond timer
- place the two microphones 2.00 metres apart using two metre rules
- place padding under each microphone to prevent sound travelling through the table
- create a sharp sound behind the first microphone
- record the time it takes for the sound to travel from microphone 1 to microphone 2
- repeat five times and calculate the mean time
- calculate the speed of sound through air by
s = 2.00 m / mean time
Bats locate their prey by echosounding.
They use pulses of ultrasound and listen for the echo with their large ears. If the time between the pulse and echo is small, the insect is closer to the bat.
Name another animal which uses echo sounding.
dolphins
When calculating the distance in an echosounding question, what is the most common error?
The distance calculated from the speed of sound and time for echo must be divided by two!
What is the human hearing range?
20 - 20 000 Hz
What is ultrasound?
Any sound over 20 000 Hz
Ultrasound is used to image babies in the womb.
An image is formed on the screen if reflections are received from the different surfaces (layers) of the baby.
How does the time for the reflection relate to the distance to the surface?
The further the surface is from the ultrasound transmitter/receiver, the longer it takes for the echo to return.
The distance to a storm can be calculated using the lightning seen and the thunder heard.
What assumption is made in this calculation?
If low frequency is low pitch sound.
What is high frequency sound?
High frequency = high pitch
What type of wave is sound?
Longitudinal
vibrations are parallel to direction of wave travel
What do waves do?
transfer energy and information without transferring matter
Dangers of microwaves?
internal heating of body tissues
If the loudness of sound increases, what also increases?
amplitude
