P12 & P13 Waves and EM Flashcards
What are the Properties of Electromagnetic Waves?
- All are transverse
- They do not need particles to travel
- All EM waves travel at a speed of 3x10^8 m/s
- They can transfer energy
- They can be reflected and refracted
- Fastest in vacumm, then gas, then liquid, then solid
What is the EM spectrum?
Radio waves - Micro waves - InfraRed waves - Visible light - UltraViolet - X-Rays - Gamma rays
As Frequency increases …..
Energy increases
Wave Length decreases
As Energy increases ……
Frequency increases
Wave Length decreases
As Wave Lenghts increase ….
Frequency decreases
Energy decreases
Uses of radio waves :
They are used in communication, long-wave radio waves are used to send information between long distances because they can defract along curved surfaces of the earth.
How does a microphone give sound out of a speaker?
1) The microphone converts sound waves into electrical signals
2) The transmitter then absorbs electrical signals causing delocalised electrons to oscilate ,this means electrical signals are converted into radio waves.
3) Then the reciever recieves radiowaves and it’s converted back into electrical signals.
How can short-wave radiowaves be recieved at long distances?
Because they can be reflected by the earth’s ionosphere.
Uses of shortwave radiowaves ….
Bluetooth devieces use short-wave radiowaves to send over short distances
A.M. and F.M. Radios use VERY short waves
How do microwaves cook food?
Water molecules in food absorbs energy from microwaves and start to move, meaning the kinetic energy of water molecules increases which heats up the food.
Why are microwaves used in satelitte communication?
Because microwaves can travel through the watery athmosphere.
What are some common uses of infrared waves?
1) Infrared ovens
2) Electrical heaters
3) Night-Vision cameras
4) Thermometre scans
What are uses of UltraViolet rays?
- Used to detect a special ink
- Flourescent bulbs
- Tanning salons to give artifical tans
What is flouresence?
Some chemicals can absorb UV radiations and emitt visible light 10 times stronger.
- this propery is used in energy effiecent bulbs
What is medical imaging?
The process of using waves to detect internal or external body strucures.
X-raya are used to detect bones & teeth
How do X-rays detect bones and teeth?
X-rays have enough energy to travel through soft tissues (such as muscles) but they can’t penetrate through bones. When X-rays hit the detector it makes the screen of the detecter black, creating a negative image of the bone.
What are some uses of Gamma rays?
1) Kill cancer cells (can also cause cancer) this is called radiotherapy
2) Kill bacteria so it’s used to sterilize surgical equipment
3) Kill bacteria in fruits to preserve them
What are the risks of EM waves?
1) Some EM waves have high energy to ionise atoms in the DNA, which can mutate it
2) Infrared and microwaves can heat up the water in tissue causing burns
3) Visible light can damge cells in the retina if stared at for too long
What are the two types of waves?
Transverse
Longitudinal
What is oscillation?
Movement between two regions in a regular pattern.
What is the period (of an osciallation)?
The time it takes for one full oscillation to happen.
What are waves?
A series of oscillations from one place to another which can transfer energy.
What is a transverse wave?
a wave where the direction of oscillation is perpendicular to the direction of energy transfer
What is a longitudinal wave?
a wave where the direction of oscillation is paralell to the direction of transfer energy
What is a medium?
A material or substance
Give an example of a transverse wave.
Ripples of water
Give an example of longitudinal waves.
Sound waves
What is the amplitude of a wave?
The maximum displacement point on a wave away from its undisturbed position
What is the wavelength of a wave?
The distance from a point on one wave to the equivalent point on the next wave
What is the frequency of a wave?
The number of waves passing a point each second
What is a longitudinal wave?
A wave that moves in the same direction as the direction in which the particles are vibrating.
What are the two key features of a longitiunidal wave?
They show areas of compression and rarefaction.
What is compression?
regions of high pressure due to particles being close together
What is rarefaction?
regions of low pressure due to particles being spread further apart
What is a transverse wave?
A wave that moves in a direction at right angles to the way in which the particles are vibrating.
What is wave speed?
The speed which a wave moves (or energy is transferred) through a medium.
How do you calculate wave speed?
Wave speed = frequency x wavelength
What is the SI unit for wave speed?
m/s
What happens when sound waves travel through a solid?
It vibrates
How can humans hear?
Sound waves cause the ear drum and other parts to vibrate. This created the sensation of sound.
What is the range of normal human hearing?
20Hz to 20,000Hz
What is ultrasound?
Sounds waves with a frequency higher than the upper limit of human hearing
How are seismic waves produced?
By earthquakes.
What are P-waves?
Longitudinal seismic waves which can travel at different speeds through a solid and a liquid
What are S-waves?
Transverse seismic waves which cannot travel through a liquid.
What is a use of P-waves and S-waves?
They can provide evidence for the structure and size of the Earth’s core.
What is the approximate range of wavelengths of electromagnetic waves?
10^-15m to 10^4m
(* Gamma to Microwaves*)
Higher the density …..
…… slower the wave
What happens when an object absorbes waves?
It gets hotter (due to the increase in energy)
