Lesson 11: Uses of EM waves

Question 1

What are radio waves used for?

2 uses…

Answer 1

1.) Television
2.) Radio

Question 2

What are microwaves used for?

2 uses…

Answer 2

1.) Satelite communications
2.) Cooking food

Question 3

What are infrared waves used for?

3 uses…

Answer 3

1.) Electrical heaters.
2.) Cooking food
3.) Infrared cameras.

Question 4

What are “visible light” waves used for?

1 use…

Answer 4

• Fibre optic communications (sending information from one place to another by using this wave.)

() - EXTRA but for understanding :)

Question 5

What are UV waves used for?

2 uses….

Answer 5

1.) Energy - efficient lamps.
2.) In sun- tan beds.

Question 6

What are X- rays and gamma rays used for?

2 uses….

Answer 6

• Medical imaging.
• Medical treatments.

Question 7

Why are radio waves suitable to be used for television and radio?

2 reasons….

Answer 7

1.) Radio waves can travel long distances before being absorbed eg. by buildings/ by trees.
2.) Radio waves reflect off a layer of charged particles in atmosphere (called ionosphere) - so the waves can be sent very long distances around the earth.

Question 8

Why are micro- waves suitable to be used for heating food?

1 reason

Answer 8

• Most food contains water molecules.
• Water molecules aborb the energy of micro- waves.
• Energy absorbed = causes temperature of food to increase.

Question 9

Why are micro- waves suitable to be used in satelite communications?

1 reason…

Answer 9

• Micro- waves can pass through the Earth’s atmosphere without being reflected/ refracted.

Question 10

Why are infrared waves suitable for being used in electric heaters/ ovens (to cook food) and for infrared cameras?

1 reason….

Answer 10

• The energy of infrared waves is easily absorbed by the surface of objects (ie. by food/ objects in a room.)

Question 11

Why is visible light suitable to be used in fibre optic communications?

Answer 11

• Visible light has a short wavelength so can carry a lot of information through the fibre optic (from one place to another.)

Question 12

Why are UV waves suitable to be used in energy- efficient light bulbs?

Answer 12

• UV waves have a shorter wavelength than visible light, so, it carries more energy than visible light.
• The energy is absorbed by internal part of bulb and converted into visible light (less energy required than normal bulb.)

Question 13

Why can X-rays and gamma rays be used in medical imaging?

Answer 13

• Very penetrative.
• X-rays: absorbed by bones –> this is why we can see them on X-rays.