EM Waves and Communication

Question 1

EM waves with different wave lengths have different _______

Answer 1

EM waves with different wave lengths have different PROPERTIES

Question 2

How many basic types of EM waves are there?

Answer 2

7

Question 3

The different regions of EM waves ______ to form a ______ _______

Answer 3

The different regions of EM waves MERGE to form a CONTINUOUS SPECTRUM

Question 4

What is the range of wavelengths of EM waves?

Answer 4

10^-5 m to more than 10^4 m

Question 5

Do EM waves all travel at the same speed through a vacuum?

Answer 5

YES

Question 6

What is the speed all EM waves travel through a vacuum?

Answer 6

3 x 10^8 m/s

Question 7

Will an EM wave with a higher frequency have a shorter wavelength or a longer wavelength?

Answer 7

An EM wave with a HIGHER frequency will have a SHORTER wavelength

Question 8

Will an EM wave with a lower frequency have a shorter wavelength or a longer wavelength?

Answer 8

An EM wave with a lower frequency will have a longer wavelength

Question 9

Because of their different properties, EM waves are used for different _______

Answer 9

Because of their different properties, EM waves are used for different PURPOSES

Question 10

Radio waves are mainly used for ______

Answer 10

Radio waves are mainly used for COMMUNICATION

Question 11

Radio waves have wave lengths longer than about ____

Answer 11

Radio waves have wave lengths longer than about 10cm

Question 12

How long are the wavelengths of long-wave radio?

Answer 12

Between 1 - 10 km

Question 13

What can long-wave radio do?

Answer 13

Be received halfway round the world from its start point

Question 14

Why can long-wave radio be picked up far from where they were emitted?

Answer 14

Because long wavelengths DIFFRACT around the curved surface of the Earth

Question 15

What 2 other things can long-wave radio also diffract around/ into?

Answer 15

1. Hills
2. Tunnels

etc

Question 16

What does the diffraction effect of long-wave radio wavelengths make it possible to do?

Answer 16

Receive radio signals even when TRANSMITTER isn’t in the LINE OF SIGHT of the RECEIVER

Question 17

What length wavelengths are the radio waves used for TV and FM radio transmissions?

Answer 17

Very short

Question 18

What effect does the short wavelength of the radio waves used for TV and FM radio transmissions on reception? Why?

Answer 18

To get reception you must be in DIRECT SIGHT of the transmitter- Doesn’t diffract around hills or travel far through buildings

Question 19

What can’t short wavelengths do that long wavelengths can?

Answer 19

Diffract around the Earth, around hills, into tunnels etc

Question 20

What is the wavelength of short-wave radio signals?

Answer 20

About 10m - 100m

Question 21

How can short-wave radio signals be received out of the line of sight of the transmitter?

Answer 21

They can be REFLECTED from the IONOSPHERE

Question 22

What is the ionosphere?

Answer 22

An electrically charged layer in the Earth’s upper atmosphere

Question 23

What type of medium-wave signals can reflect from the ionosphere

Answer 23

The SHORTER ones

Question 24

What does reflecting medium-wave signals off the ionosphere depend on? (2)

Answer 24

1. Atmospheric conditions

2. The time of day