Microwaves And Infrared Flashcards
why are different wavelengths of microwave radiation used in communications and microwave ovens despite them both using microwaves
- in communications, microwaves need to pass through the earths watery atmosphere
- but in microwave ovens, the microwaves need to be absorbed by the water molecules in the food
- this requires different intensities of microwaves
how do microwaves heat up food
- the microwaves penetrate a few centimetres into the food
- before being absorbed and transferring their energy to the water molecules in the food
- causing the water to heat up
- water molecules transfer the energy to the rest of the food by heating which quickly cooks the food
what is another way of explaining how microwaves heat food up
- they cause the water molecules in the food to vibrate
- due to the transfer of energy into the kinetic energy stores of the water
- leading to the generations of heat
- which is then transferred to the thermal energy stores of the food molecules
what is infrared radiation generally given out by and what does its intensity depend on
- any object with a temperature (specifically hot ones)
- its intensity id dependent on the temperature of the object
- so the hotter the object
- the more IR radiation is given out
what can infrared cameras be used for
- to detect infrared radiation
- and to monitor temperature
how do infrared cameras show us a visual image of the IR radiation and what is this called
- the camera detects the IR radiation and turns it into an electrical signal
- which is displayed on a screen as a picture
- this is called thermal imaging
what do the police use infrared cameras for
to see suspects that are trying to escape of hide in the dark
how can infrared sensors be used in security systems
- if infrared radiation is detected
- an alarm sounds or a security light turns on
what does the absorption of infrared radiation cause an object to become
hotter
how is infrared radiation used to cook food
- when the food absorbs IR radiation
- the temperature of the food increases as a whole
- like the heating element of a toaster
what is the difference between how infrared and microwave radiation heat or cook food
- infrared radiation would naturally heat up the surface of the food first, heating it from the outside-in
- whereas microwave radiation heats up the water molecules in the food, heating it from the inside-out
- infrared radiation also heats up the whole food indiscriminately
- whereas microwave radiation specifically heats up the water molecules in the food first
how do electric heaters heat a room
- electric heaters contain wire that heats up when a current flows through it
- the wire emits lots of infrared radiation and a little visible light as it glows
- the emitted IR radiation is absorbed by the air in the room, causing the generation of a convection current
- energy is transferred by the IR waves to the thermal energy stores of the objects in the room, causing their temperature to increase
what can infrared radiation alternatively be used to do
transfer information
what is an example of infrared radiation being used to transfer information
it can be used to send files between mobile phones or laptops
what conditions have to be met in order for infrared radiation to be sued as an efficient method of information transmission
- the distance between the devices sharing information must be fairly small
- and the receiver must be in the line of sight of the emitter
- such as a tv remote only working when pointing at the tv
