P1 - EM receivers, Analogue and Digital, Humans & the Environment, Seismic Waves

Question 1

What are Radio waves and microwaves useful for?

Answer 1

They are useful for transferring information over long distances.

Question 2

Why are Radio-waves and microwaves better at transferring information over longer ranges?

Answer 2

• They don’t get absorbed by the Earth’s atmosphere as much as waves in the middle of the EM spectrum ( like heat for example ), or those at the high frequency end of the spectrum.

Question 3

What are Radio-waves?

Answer 3

Radio waves are EM radiation with wavelengths longer than about 10 cm.

Question 4

Why are Long wave radio waves able to be received halfway around the world? 1 - 10 km

Answer 4

• Long wave radio wavelengths ( 1 - 10 KM ) can be transmitted from one place and received halfway round the world because they diffract around the curved surface of the Earth.

Question 5

What is a disadvantage of Radio-waves used for TV and FM radio waves? 10cm - 10 km

Answer 5

They have very short wavelengths ( 10 cm - 10 m ).
To get reception you must be in direct sight of the transmitter - the signal doesn’t bend around hills or travel far through buildings.

Question 6

Why are short wave radio signals with wavelengths of about 10 m - 100m be received at long distances?

Answer 6

• They can be received at long distances from the transmitter because of reflection in the ionosphere.
• Depending on the atmospheric conditions and time of day, medium wave signals

Question 7

What is diffraction?

Answer 7

Diffraction is when the waves spread out at the edges when they pass through a gap or past an object.

Question 8

What does the amount of diffraction depend on?

Answer 8

The amount of diffraction depends on the wavelength of the wave, relative to the size of the gap or obstacle.

Question 9

Why do longer wavelengths encounter a lot of diffraction?

Answer 9

• Longer wavelengths can be larger than the object/obstacle/gap and therefore much diffraction will occur.

Question 10

Why are longer wavelengths useful for communication?

Answer 10

• They can diffract more, so they an bend around corners and any obstacles such as hills and tall buildings.
• Longer wavelengths can travel long distances between the transmitter and receiver without them having to be in the line of sight of each other.

Question 11

Why do shorter wavelength transmitters have to be high up?

Answer 11

• They must avoid any obstacles to make sure wave reaches its destination.

Question 12

Where can diffraction occur on the satellite dish?

Answer 12

• They can occur at the edges of the dishes used to transmit signals this often results in signal loss.
• If the wave is more spread out so the signal is weaker.

Question 13

When would a wave change speed?

Answer 13

• When a wave comes up against something that has a different density it changes speed.

Question 14

What is refraction?

Answer 14

• When a wave comes up against something that has a different density it changes speed.
• If the wave hits the new substance at an angle, it changes direction this is refraction,