Microwaves and Infrared

Question 1

Which type of EM wave is used for cooking and home security systems?

Answer 1

Infrared

Question 2

True or false? The hotter an object is the less infrared radiation it gives out

Answer 2

False

The hotter the object is the more infrared radiation it gives out

Question 3

Give an example of where infrared waves are used to transfer information over short distances

Answer 3

In remote controls

Question 4

How do optical fibres carry data?

Answer 4

Signals made up of pulses of infrared radiation are sent along optical fibres

Question 5

Describe how infrared radiation is used in thermal imaging.

Answer 5

Infrared cameras detect infrared radiation and turn it into an electrical signal, which is displayed on a screen as a picture showing hot and cold areas.

Question 6

Describe how electric heaters warm up rooms

Answer 6

Electric heaters contain a long piece of wire that heats up when a current flows through it. The wire emits infrared radiation which is absorbed by objects and the air in the room. This transfers energy to the thermal energy stores of the objects and the air, causing their temperature to increase

Question 7

Explain why the wavelengths of microwaves used in microwave ovens are different from the wavelength of microwaves used in satellite transmissions

Answer 7

The microwaves used in satellite transmission need to pass through water in the Earth’s atmosphere, but in microwave ovens the microwaves need to be absorbed by the water molecules in the food being cooked. The difference in wavelength determine whether or not the microwaves are absorbed by water molecules