EM Waves' Dangers And Uses Flashcards
radiowaves uses
transmit television and radio programmes
radiowaves dangers
large doses cause cancer and leukuemia
microwave uses
heat up food and use in mobile phones
microwaves dangers
internal heating of body tissue
infared uses
remote controls and recorders
infared dangers
heat causes skin cancer and burns
visible light uses
light up environment
visible light dangers
blinding of eyes and thermal heat if concentrated
ultraviolet light uses
killing microbes and makes clothes glow
ultraviolet dangers
severe burns and damage to cells
x ray uses
see inside people and airport security
x ray dangers
damage cells and cause mutations
gamma ray uses
kill cancer cells and radiotherapy
gamma ray dangers
cause genetic mutation
why dont we need satellites for radiowaves
- because radiowaves are reflected back to earth by the ionosphere
- this is because its frequency is too low so it therefore doesnt have enough power to escape
why do microwaves need satellites
- because microwaves penetrate the ionosphere
- so they dont hey bounced back to earth
- this means that we need something to transmit them back which is a satellite
how do infared and microwaves heat up food differently
- infared waves heat up the surface of food
- where as microwaves penetrate a few centimeters into the food
- vibrate the water molecules in food, heating it from the inside
why do we use radiotowers for phones
- distance from cell phone to tower is a few miles
- so less power is used transmit and receive signals
- long distances add to delay in communication and reduced quality of service
with long radio waves, why can radio signals be recieved even though the reciever isnt in the line of sight of the transmitter
- their wavelengths of 1 to 10km can be recieved halfway around the world from where they started
- because long wavelengths tend to bend around the curved surface of the earth
how do micro wave oven heat up food quickly
- the microwaves penetrate into the food
- before begin absorbed and and transferring energy they are carrying to the water molecules in the food
- causing the water heat up
- water molecules transfer the energy to the rest of the molecules in the food internally, quickly heating the food
