Electromagnetic Waves Flashcards
Order from longest wavelength
- radio waves
- microwaves
- infra red
- visible light
- ultra violet
- x rays
- gamma rays
Order from highest frequency
- gamma rays
- x rays
- ultra violet
- visible light
- infrared
- microwaves
- radio waves
What type of wave are electromagnetic waves
Transverse waves
What’s the relationship between wavelength and frequency
They are inversely related
What does ionising mean
Damaging to our cells
Which waves are ionising
- ultraviolet
- X rays
- gamma rays
What can happen to electromagnetic waves when interacting with other objects
They can be absorbed, reflected or transmitted
Which type of electromagnetic waves can be used in communication
- radio waves
- microwaves
What are electromagnetic waves made up of
Oscillating electric and magnetic fields
How do radio waves generate electricity
They use alternating currents
- made up of oscillating charges
What device do you use to generate radio waves
Transmitter connected to an oscilloscope
What is an oscilloscope used for
To see the frequency of an alternating current
What does an alternating current do
Determines the frequency of the wave
What is the name of the device in which we detect the generated radio wave
Receiver connected to an oscilloscope k
Radio waves -
The frequency generated is the same as the frequency received what does this allow us to do
Allows us to transfer information
What is the main use for radio waves
Communication
How far can long radio waves travel
HUGE distances
How far can short radiowaves travel
Long distances
How do very short radio waves travel
Directly from the transmitter to the receiver
How do long radio waves travel
Distract (bend) around the curved surface of the earth
How do short radio waves travel
Reflected off the ionosphere
What is the ionosphere
Electrically charged layer of the upper surface
What are microwaves that aren’t absorbed by water molecules used for
Communication
What is the use for microwave that are absorbed by water
To heat up our food
How do microwaves that aren’t absorbed by water work
Using satellites
Microwaves have to pass through the earths atmosphere
Once they reach the satellite they’re received and then transmitted back to earth
On Earth we detect them using a satellite dish
How do microwaves that are absorbed by water work
In microwaves - microwaves are fired at our food
The heat from the waves get absorbed by the water molecules
As the water molecules vibrate more they transfer energy to the neighbouring molecules
So it spreads throughout the food via conduction and convection
What is infrared radiation
Radiation emitted from all objects that have thermal energy
What’s the relationship with infrared radiation and heat
The hotter an object is the more infrared radiation will be emitted
What are 3 uses of infrared radiation
Infrared camera
Cooking
Electric heaters
How does an infrared camera work
See in the dark to spot living organisms
Organisms will appear bright as they are hotter so emit more radiation
How does an oven work using infrared radiation
Heat up the oven which emits infrared radiation
Heat up the food by transferring the heat energy
Why in an oven does food crisp but in a microwave it will only continue to get hotter
Infrared radiation doesn’t penetrate the surface of the food causing it to crisp
Microwaves do penetrate and absorb the water molecules
How do electric heaters work
Use electrical energy to heat up the metal of the heater
So hot it emits infrared radiation to the surroundings
Heat up rooms
Are microwaves and infrared radiation harmful
Only in high quantities
What is the colour of the longest wavelength for visible light
Red
What is the colour of the shortest wavelength for visible light
Violet
What does ROYGBIV stand for
Red
Orange
Yellow
Green
Blue
Indigo
Violet
How do we see different colours
Light we use to see appear different colours depending on the wavelength
What can visible light be used for
Communication
Through optical fibres or
Copper wires and electricity
How do optical fibres work
They are thin glass or plastic
Can transmit pulses of light long distances
The light is reflected every time it hits the surface
Why are optical fibres good
They can transmit data quickly
Can transmit more info than copper wires
Less likely to be distorted than copper wires
What materials need to be used for transmitting visible light
Materials that will reflect the light - not absorbing
Reflection is specular - NOT diffuse
Instead of optical fibres what can be used
Copper wires and electricity
Does uv have a higher or lower frequency than visible light
Un has a higher frequency than visible light
Does uv have a longer or shorter wavelength than visible light
Uv has a Shorter wavelength than visible light
What are 4 uses for uv
Most common: sun emits uv - get a tan/burn
Fluorescence
Security
Sterilise water
How does fluorescence work
UV light is absorbed
Energy is re emitted as visible light
How do fluorescent slights work
Generate uv
Absorbed by a layer of phosphorus that cotes the inside of a glass bulb
So much energy it re-emits the energy as visible light
What’s a benefit of fluorescent lights
Energy efficient
What’s the use of uv in security
Security pens - write codes that are completely invisible until we shine a uv light on them
Can do the same with passports and bank notes (money)
How is uv used to sterilise water
Destroys microorganisms
What are x rays used for
To view the internal structure of objects
(Eg. Our bodies)
How does an x ray machine work
By firing x rays through a persons body
Recording the rays that get through using a detecter plate
The x rays are absorbed by bones
They only pass partially through fleshy parts eg heart
Image starts off white
Goes black if that area of the detector plate receives radiation
What colour are bones shown as on x rays
White
What are x rays used for
Detect broken bones
Detect other diseases
Are x rays harmful
A bit, they give a person a small amount of radiation
(Most of the time it’s worth taking the risk)
Who experience the most danger when x rays are being fired
The staff involved
What do the staff do to prevent from the harm of x rays
Leave the room
Wear a lead lined apron
What’s a benefit of doing an x ray
It’s a quick cheap test
What are gamma rays used for
Used for medical imaging
Used to treat cancer (radiotherapy)
Used to sterilise things eg medical equipment/ food
What’s a benefit of gamma rays
They can destroy microorganisms without causing any other damage
Positive about using gamma rays to kill microorganisms on food
Keeps food fresh for longer still face to eat
Positive of gamma rays and x rays in medicine
Can help us diagnose and treat diseases
Negatives of gamma rays and x rays in medicine
Both are ionising radiation
Can damage our cells
Can lead to cancer
