Cooking with waves

Question 1

What factors make infrared useful for cooking?

Answer 1

The warmer an object gets, the more infrared it emits. If an object absorbs infrared radiation its surface gets hotter.

Question 2

How does a toaster work?

Answer 2

As the toaster gets hotter, it emits more infrared. It emits some red light. The infrared waves from the toaster are then absorbed by the food. This heats up the surface of the food and so it gets cooked.

Question 3

Why do grills and toasters have shiny bottoms?

Answer 3

This helps reflect the infrared back towards the food so that it gets cooked even more quickly

Question 4

What are microwaves?

Answer 4

Wave that fits between radio waves and infrared in the electromagnetic spectrum

Question 5

How do microwave ovens work?

Answer 5

A microwave oven produces a steady stream of microwaves. Instead of just heating the surface of the food, they travel about 1cm into the food. The microwaves are absorbed by fat and water inside the food. The food heats up. Shiny metal surfaces reflect microwaves so that all parts of the food are heated.

Question 6

Effect of microwaves to humans

Answer 6

cause burns to humans, as they are absorbed by body tissue just as they are absorbed by food in microwave ovens.

Question 7

How to prevent microwaves causing damage in microwave ovens

Answer 7

They can pass through glass and plastics, and so to prevent the microwaves causing damage, a metal mesh is placed inside the oven door.

Question 8

How energy is transferred

Answer 8

From electromagnetic waves to the molecules inside or on the food. This energy is then transferred to the rest of the food through convection and conduction

Question 9

Energy transfer in microwave ovens

Answer 9

The fat and water molecules inside the outer layers of the food gain kinetic energy as they absorb the microwaves.

Question 10

Energy transfer in infrared

Answer 10

Only the particles on the surface of the food gain kinetic energy as they absorb the infrared waves