P1 - Cooking and communicating with waves

Question 1

How does infrared radiation cook food?

Answer 1

• it does not penetrate very far into the food
• it only heats the surface of the food
• all particles absorb energy
• energy is transferred by conduction through the food

Question 2

How do microwaves cook food?

Answer 2

• penetrate about 1cm into the food
• water and fat molecules vibrate more
• kinetic energy increases
• energy transferred to the food by conduction

Question 3

What are the issues with communicating with microwaves?

Answer 3

The transmitter and receiver need to be in a line of sight, which is lost due to the curvature of the earth.

Question 4

What is an atmospheric duct?

Answer 4

A horizontal layer in the lower atmosphere in which the vertical refractive index gradients are such that waves tend to follow the curvature of the Earth.

Question 5

How can signal be lost?

Answer 5

• bad weather
• little diffraction in hills
• interference