P3.3.4 Detecting messages

Question 1

What is a carrier wave?

Answer 1

A wave that carries information

Question 2

Which types of electromagnetic radiation can be used as carrier waves?

Answer 2

Radio waves, microwaves and infrared

Question 3

Describe how the sound of a radio presenter travels from the microphone to your radio?

Answer 3

1) Microphone converts sound into an electrical signal 2) This signal is converted into a digital signal of 1s and 0s 3) Transmitter adds the digital signal to the carrier wave 4) This is modulation. The transmitter the changes the amplitude or frequency of the carrier wave. 5) Carrier wave is broadcast and travels across the country as a radio wave. 6) A radio set is tuned to the same frequency as the carrier wave. 7) Radio set converts the radio signal back into sound. 8) The loudspeaker plays the programme

Question 4

Describe the difference between AM and FM

Answer 4

AM is amplitude modulation - it means changing the amplitude to represent 1s and 0s. FM is frequency modulation - it means changing the frequency of the carrier wave

Question 5

What is modulation?

Answer 5

Changing the amplitude or frequency of a wave

Question 6

What is diffraction?

Answer 6

Spreading out of waves around an obstacle or going through a gap

Question 7

What is the connection between Hertz (Hz) and mega Hertz (MHz)?

Answer 7

1 MHz = 1 000 000 Hz

Question 8

What is the connection between Hertz (Hz) and kilo Hertz (MHz)?

Answer 8

1 kHz = 1000 Hz

Question 9

How can you calculate wavelength?

Answer 9

Wavelength = wave speed / frequency

Question 10

What is an SI unit?

Answer 10

A unit that is used internationally to allow scientists all over the world to compare their data.

Question 11

A radio wave is used to the find the position of an aircraft on a runway. It takes 0.000 002 seconds for the radio waves to travel from the control tower to the aircraft and back. Calculate how far away the aircraft is from the tower. Radio waves travel at 300 000 000 m/s

Answer 11

300 000 000 x 0.000 002 = 600m 600m / 2 = 300 metres

Question 12

This method can be used to find distances to planets within our Solar System. Calculate the time it would take to receive a radio signal sent from Earth that reflects off Venus. Use the speed of radio waves above. The average distance to Venus = 108 000 000 000 m

Answer 12

2 x 108 000 000 000 = 216 000 000 000 m (there and back) Time = distance / speed 216 000 000 000 / 300 000 000 = 720 seconds

Question 13

What is the connection between speed, distance and time?

Answer 13

Speed = distance/time

Question 14

How can you calculate distance?

Answer 14

Distance = speed x time

Question 15

How can you calculate time?

Answer 15

Time = distance / speed

Question 16

Draw a diagram to show radio waves diffracting around hills towards a house.

Answer 16