Electromagnetic Spectrum Flashcards
As wavelength increases, what happens to the frequency?
Frequency decreases
Why do digital signals give better quality reception?
The noise is more easily removed (through regeneration)
Speed of EM waves
All parts of the EM spectrum waves travel at the same speed in free space
This speed is the speed of light (300 000 000 m/s)
Uses of radio waves 3
Broadcasting & communications
Satellite transmissions
Uses of microwaves
Mobile phones, satellite transmission & cooking
Infrared uses 3
Heaters, night vision & remote controls
Visible light uses 2
Optical fibres & photography
UV uses 4
Fluorescent lamps eg tanning machines, disinfecting water, security markings eg for Chas king banknotes
X ray uses
Observing the interval structure of objects & materials(not just medical applications)
Gamma rays uses
Sterilising medical equipment, food & radiotherapy
Effects of over exposure to microwaves
Internal heating of body tissue
Effects of over exposure to infrared
Surface burns to skin
Effects of over exposure to UV
Damage to skin cells at the surface & to retinal damage
Effects of over exposure to X rays & gamma rays
Killing & mutation of cells
Cancer
What happens when electromagnetic radiation from the sun arrives at the earths atmosphere?
Some reflected
Some transmitted to earths surface
Some absorbed by atmosphere
Types of electromagnetic radiation that arrive at the earths surface
High energy infrared
Visible light
Low energy ultraviolet
Properties of radio waves & microwaves 3
- They are reflected by metal surfaces
- They heat materials if they can make particles in the material vibrate
- The amount of heating depends on the power of the radiation & the time that the material is exposed to the radiation
How are people exposed to microwave radiation through their phones? 2
To the head from the aerial in the phone
To the body from transmitters in base station masts
Radio waves emitted & detected
Emitted by a transmitter & detected by an aerial
Why does food cook more quickly in a microwave
Water molecules in the food absorb the microwaves and become very hot
Food therefore cooks throughout rather than just from the outside
Give one confirmation that microwaves can pass through glass, brick and so on
We are able to use mobile phones almost anywhere at work or home
How do microwave ovens prevent human body tissue from also being heated
They have metal screens that reflect microwaves and keep them inside the oven
Why don’t mobile phones cook your brain
The microwaves used transmit much less energy than those used in a microwave oven
Why can we use x rays to check a patients bones
X rays pass easily through soft body tissue but cannot pass through bones
