Waves, Density and Pressure Flashcards
Equation for wave speed.
wave speed = frequency x wavelength
m/s Hz m
Time period =
1 over frequency
What is the frequency range of human hearing
20 - 20,000 Hz
What is the main characteristic of waves
All waves transfer energy, but they do not transfer the particles of the medium
This means when a wave travels between two points, no matter actually travels with it, the points on the wave just vibrate back and forth about fixed positions
Tip about how to accurately count wavefronts/ waves from birds eye view.
Count from 1 to the next, instead of counting each individual one.
Describe an investigation to calculate the speed of sound.
Trundle Wheel- 100m between 2 people
One person will bang wooden blocks against each other
Second person has a stopwatch and starts it when they see the bang, stop it when they hear the sound,
Calculate speed with speed= distance over time
What are the problems and how could you fix them with the investigation (speed of sound)
Measurement of time : Ensure to take repeat readings when timing intervals and calculate an average to keep this error to a minimum
Maximise the distance between the two people where possible. This will reduce the error in measurements of time because the time taken by the sound waves to travel will be greater
Explain the problems with using a stopwatch.
For example, if a manual stopwatch is being used there could be variation in the time measured which can be up to 0.2 seconds due to a person’s reaction time
The time interval could be as little as 0.3 seconds for sound travelling in air
This means that the variation due to the stopwatch readings has a big influence on the results and they may not be reliable
Use of Radio Waves
Communication and broadcasting (Radio and TV)
Uses of microwaves
Satellite communication and cooking.
Uses of infra-red waves
Remote controls
Thermal imaging (Medicine and Industry)
Electric Heaters
Heating or Cooking things
Night Vision equipment
Uses of Visible light
Optical fibres
Photography
Uses of Ultra-Violet
Fluorescent lighting
Tanning
Security marking (Detecting counterfeit money)
Uses of X-rays
Imaging internal structures of the body and other objects.
Uses of Gamma Rays
Used to sterilise medical equipment (gamma kills bacteria)
If aimed at cancerous tissue they can kill it
How does wavelength affect the danger of Electromagnetic waves?
As wavelength becomes shorter, danger increases.
Danger of Radio Waves.
None
Dangers of Microwaves and how to prevent them.
Internal heating of body tissue
Dangers of Infra-red and how to prevent them.
Skin-burns/ burning tissues and skin
Dangers of Visible Light and how to prevent them.
Bright light can cause eye damage.
Dangers of Ultra-Violet and how to prevent them.
Blindness - Good quality sunglasses absorb this light and prevent it from damaging the eye
Damage to surface cells/ skin damage - Sunscreen absorbs this light and prevents it from damaging the skin.
Dangers of X-Rays and how to prevent them.
Long-term exposure can cause cancer - When used in medical industry level is low, Doctors leave room to avoid unnecessary exposure.
Cell mutation -
Dangers of Gamma Rays and how to prevent them.
Cancer, gamma rays are ionising - People in contact with Gamma Rays are routinely tested for their radiation levels. badges are worn. Wear protective clothing and avoid contact with bare skin. Person is only exposed to low-levels.
Cell mutation -
Density =
kg/m3
mass over volume
kg m3
Pressure =
N/m2 or Pa
force over area
N m2
Pressure difference =
n/m2
height x density x gravitational field strength
m kg/m3 N/kg
What is the density of water?
1000 kg/m3
1 g/cm3
1m3 in cm3 =
1,000,000 cm3
1m2 in cm2 =
10,000 cm2
Things to remember in questions involving different units.
1m3 does not equal 100cm3
Examples of Transverse waves
Light, electromagnetic waves, Water Waves, S seismic waves
Examples of Longitudinal Waves
Seismic P Waves
Sound Waves
Describe the vibrations of Longitudinal waves.
Vibrations are parallel/ in the same direction that the wave travels/energy transfer.
Describe the vibrations of Transverse waves.
Vibrations are 90o to the direction that the waves travel/energy transfer.
What is oscillation?
Vibrations
How to convert 48m^3 into cm^3.
48 x1,000,000 = 48000000
How to convert 22,000 cm^3 into m^3.
22,000 divided by 1,000,000 = 0.022
1m^3 = 1 x 10^6 cm^3
