Simplified P1 - Cooking and Communicating Using Waves & Data Transmission

Question 1

What is infrared radiation?

Answer 1

All objects emit (give out) and absorb (take in) thermal radiation, which is also called infrared radiation.

Question 2

Can infrared radiation penetrate food?

Answer 2

Infrared radiation can penetrate food, however not very easily.

Question 3

How far can microwaves penetrate into food?

Answer 3

Microwaves can penetrate up to 1 cm into food.

Question 4

What materials can microwaves penetrate, and what materials can they not?

Answer 4

Microwaves can penetrate glass or plastic but are reflected by shiny metal surfaces:

• special glass in a microwave oven door reflects microwaves
• they can cause body tissue to burn.

Question 5

How is energy transferred?

Answer 5

Energy is transferred through waves.

Question 6

How is the amount of energy transferred affected?

Answer 6

The amount of energy depends on the frequency or wavelength of the wave, higher frequency waves with a short wavelength waves transfer more energy.

Question 7

How do normal ovens cook food?

Answer 7

Normal ovens cook food by infrared radiation:

• energy is absorbed by the surface of the food
• the kinetic energy of the surface food particles increases
• the rest of the food is heated by conduction.

Question 8

How do microwaves cook food?

Answer 8

Microwave ovens cook food by microwave radiation:

- the water or fat molecules in the outer layers of food vibrate more.

Question 9

What is the range for the wavelengths of microwaves?

Answer 9

Microwaves have wavelengths between 1 mm and 30 cm.

Question 10

How do mobile phones lower the amount of energy transferred to you?

Answer 10

Mobile phones lower the amount of energy transferred to you by using longer wavelengths.

Question 11

What is another use of Microwaves besides cooking food?

Answer 11

Microwaves can be used to communicate over long distances.

Question 12

What is one condition required for microwave communication?

Answer 12

The transmitter and receiver must be in line of sight, this is why Aerials are normally situated on top of high buildings.

Question 13

What do satellites do with Microwaves?

Answer 13

Satellites use microwaves for communication.

Question 14

How do satellites use Microwaves for communication?

Answer 14

Satellites are used for microwave communication.
– The signal from Earth is received, amplified and re-transmitted back to Earth.
– Satellites are in line of sight because there are no obstructions in space.
– Large aerials can handle thousands of phone calls and television channels at once.

Question 15

What are some concerns about where phone masts are located?

Answer 15

Some concerns are that phone masts may be too close to locals and schools, as they can cause harm to the locals or school children.

Question 16

How does signal strength for mobile phones change change over distance?

Answer 16

Signal strength for mobile phones can change a lot over a short distance, through these factors:
– Microwaves do not show much diffraction.
– Adverse weather and large areas of water can scatter the signals.
– The curvature of the Earth limits the line of sight so transmitters have to be on tall buildings or close together.

Question 17

Why are mobile phones banned in planes and hospitals?

Answer 17

They can interfere with sensitive equipment.

Question 18

What do infrared signals do?

Answer 18

Infrared signals carry information that allows electronic and electrical devices to be controlled.

Question 19

How do LEDs work on remotes?

Answer 19

Pressing a button on the remote control device
completes the circuit. A coded signal is sent to a light
emitting diode or LED at the front of the remote, these can have different signals, there may be a signal for a start command, instruction command, stop command or even a device code.

Question 20

What does the device ( Television in this case ) do with LEDs?

Answer 20

The LED will transmit pulses, which are received by the television which are then decoded allowing the television to change volume or channel for example.

Question 21

What are the advantages of digital signals over analogue signals, for use in television?

Answer 21

Some advantages are:
– improved signal quality for both picture and sound
– a greater choice of programmes
– being able to interact with the programme
– information services such as programme guides and subtitles.