Microwaves and infrared

Question 1

What are the characteristics of microwaves and infrared

Answer 1

• Microwaves and infrared radiation (IR) are second and third on the EM spectrum
• They both have long wavelengths and short frequencies

Question 2

What are microwaves that are absorbed by water used for

Answer 2

• Used to send and receive information from satelites
• As the Earth’s atmosphere contains many water molecules, we must make sure that the waves are not absorbed by them
• When the satelite receives information and transmits it back to Earth (using microwaves), we receive it using satlite dishes
• This is used in satelite TV

Question 3

What are microwaves that are absorbed by water used for

Answer 3

• Used in microwave ovens
• Microwaves are emitted which are absorbed by water molecules in the food. As they have more energy, they vibrate more. This passes energy on to neighbouring molecules which heats up the food (heat spreads through conduction and convection)

Question 4

What is infrared radiation

Answer 4

• Emitted by all objects that have thermal energy
• The hotter the object, the more infrared radiation is emitted

Question 5

How do infrared cameras work

Answer 5

• Helps us to see in the dark
• Captures infrared radiation emitted by all objects
• Allows us to see living organisms as they are hotter than their surroundings and therefore, they emit more infrared radiation

Question 6

How is infrarred used in cooking

Answer 6

• Metal is heated to high temperatures (in ovens and grills)
• Metal emits lots of infrared radiation
• This radiation is absorbed by the food and added to its thermal energy store. This inturn heats up the food
• IR doesn’t penetrate the surface of the food (bread becomes toast rather than just heating up)

Question 7

When is IR and microwaves harmful

Answer 7

• Only harmful in large quantities
• E.G: putting a living organism inside a microwave oven