EM waves and communication

Question 1

What is the order of EM waves? (longest-shortest) (7)

What are their wavelengths?

Answer 1

Radio waves (1m - 10⁴ m), Micro waves (10⁻²m = 1 cm), Infrared (10⁻⁵ m), Visible Light (10⁻⁷ m), Ultra Violet (10⁻⁸ m), X-rays (10⁻¹⁰ m), Gamma rays (10⁻¹² m)

Question 2

All the EM waves travel at the same speed ([ ]) in a [ ]

Answer 2

3 * 10⁸ m/s

vacuum

Question 3

EM waves with higher frequencies have [ ] wavelengths

Answer 3

shorter

Question 4

EM waves with [ ] frequencies have shorter wavelengths

Answer 4

higher

Question 5

Why can long-wave radio be transmitted all around the world?

Answer 5

It’s wavelength = 1-10km

It can diffract around the curved surface of he earth and also around hills, into tunnels etc.

Question 6

Describe the requirements for TV and FM radio. Why?

Answer 6

Very short wavelengths = 10cm - 10m

To get reception, you must be in direct sight of the transmitter.

Question 7

How can short-wave signals be received at long distances from the transmitter?

Answer 7

They reflect from the ionosphere - an electrically charged layer in the Earth’s upper atmosphere

Question 8

Medium wave signals can also reflect from the ionosphere, depending on [ ] and the time of day

Answer 8

atmospheric conditions