EMR Flashcards
What is the wavelength?
The distance between two successive waves
What is the amplitude?
The maximum distance a wave extends beyond its middle position
What is the wave equation?
If the frequency of a wave increases, the wavelength decreases and vice versa
How is electromagnetic radiation produced?
When electrical charges move a magnetic field is generated and vice versa
What are the different types of EMR radiation?
Radio waves, microwaves, infrared, visible light, ultraviolet, x rays and gamma rays
What speed do all EMR waves travel at?
300,000 km/s
What are the different colours in the visible light spectrum?
Red, orange, yellow, green, blue, indigo, violet
What is white and black light?
White light is all the colours in the visible spectrum, black light is the absence of colour
Why do we see objects in colour?
Because all objects absorb some colours and reflect some e.g a red apples reflects red and absorbs every other colour
What are the three primary colours?
Red, green and blue
What are the three secondary colours?
Cyan, magenta and yellow
How does colour blindness work?
We have three cones in our eyes for the three different primary colours and if one doesn’t work then we don’t see that colour
What happens when we mix different pigments?
We are subtracting wavelengths so we are doing colour subtraction
What happens when we mix light?
We are adding extra wavelengths so it is colour addition
What types of communication use radio waves?
Television and radio networks
How do short-wave radio signals work?
The waves beam upwards at an angle and are reflected off the ionosphere back onto earth
Why are long radio waves good for communication?
Because they can bend around the Earths surface
How do AM and FM waves travel?
By using a carrier wave
How do carrier waves work?
They travel along with the radio wave and after being detected by the antenna of a radio they are subtracted, leaving just the audio signal
What happens in AM waves when the carrier is subtracted?
The frequency stays the same as the carrier but the amplitude varies
What happens in FM waves when the carrier is subtracted?
The amplitude is the same as the carrier but the frequency varies
Which have a shorter wavelength: FM or AM?
FM
Why are AM waves used more often?
Because they can travel around large obstacles more easily than FM waves and can also travel further
What is frequency?
The number of waves produced each second
What are microwaves used for?
In radar and communications systems and also sometimes cooking
Why are microwaves used in cooking?
Because they are absorbed by the food, causing the molecules to heat up
What materials don’t absorb or reflect microwaves?
Glass, paper and plastics don’t absorb and metals reflect.
How is it heat transferred from the sun to the Earth?
By infrared radiation
What are the two types of signals?
Analogue and Digital
What signal do we use most often?
Digital
What type of number systems do digital signals use?
The binary number system (0’s and 1’s or ons and offs)
How does optic fibre work?
Digital light pulses from a laser, travels along glass fibres being reflected inside the fibre
How do ADSL modems work?
They send digital signals down copper wires designed for analogue signals. A splitter is used to split the analogue from the digital
What type of EMR wave do mobile phones use?
Microwaves
How do mobile phones work?
Each phone sends the message by line of sight to a base station. The message is moved between base stations using copper cable or optic fibre
How does television work?
It is transmitted by UHF and VHF radio waves. They use digital signal because it is more reliable
What is the wavelength of a radio wave?
1m-2km
What are radio waves used for?
Radio and TV channels and communication
What is the wavelength of microwaves?
1mm-1m
What are microwaves used for?
Cooking and communication such as mobile phones and the Internet
What is the wavelength of infrared radiation?
750nm-1mm
What is infrared used for?
Getting heat from the sun to the earth and night-vision
What is the wavelength of Visible Light?
750nm-480nm
What is visible light used for?
Enables us to see things (duh), DVD players and lightbulbs
What is the wavelength of ultra violet waves?
480nm-100nm
What is ultra violet used for?
Sun tanning, killing microbes, sterilising food and detecting forged bank notes
What is the wavelength of X-Rays?
100nm-10nm
What are X-Rays used for?
See inside people and airport security
What is the wavelength of Gamma Rays?
10nm-10pm
What are gamma Rays used for?
Kill cancer cells-radiotherapy, sterilise food and medical equipment
