Paper 1 - Wave Behaviour

Question 1

What type of wave are electromagnetic waves ?

Answer 1

Electromagnetic waves are transverse - they are composed of an electric field and a magnetic field at right angles to one another

Question 2

Behavior of EM waves

Answer 2

• May be reflected off a surface
• refracted when they move from one material to another
• transmitted when they pass through a material
• absorbed by different materials. E.g. UV absorbed by the skin, but not by the earth’s atmosphere.
  [DEPENDS ON MATERIAL AND WAVELENGTH OF EM WAVE]
  Waves travel in straight lines unless reflected or refracted. - refracted due to change in velocity

Question 3

Wave boundaries at the ionosphere

Xray, gamma, microwave, radiowave

Answer 3

• X-rays and gamma rays cannot reach the surface of the earth as they are absorbed by the upper atmosphere.
• Microwaves are transmitted by the ionosphere and then re transmitted back to the receiver.
• Most radio waves not transmitted by ionosphere. They are refracted and then reflected to the receiver

Question 4

Radio wave oscillations - along metal poles

Answer 4

Radio waves produced by oscillations (variations in current and voltage) when current moves up and down in the aerial in electrical circuits. A metal rod or wire can be used as an aerial to receive radio waves. Oscillations cause radio waves to spread out from the aerial.The radio waves are absorbed by the metal and cause oscillations in electrical circuits connected to the aerial. - oscillating current . Oscillations travel from transmitting to receiving aerial / circuits.

Question 5

What affects do density have on the velocity of EM waves ? Speed of light in a diamond ?

Answer 5

EM waves have different velocities in different materials, linked to density. Speed of light in a diamond 40 % of that in air / a vacuum. Due to high optical density.

Question 6

(WORKED EXAMPLE) Explain why it is not possible to get a suntan inside the house, but it is possible to listen to the radio ?

Answer 6

UV rays from the sun not transmitted by the walls of the house, they are absorbed. Radio waves are transmitted by the walls so can be detected by a radio receiver inside the house

Question 7

What are oscillations?

Answer 7

Variations in current and voltage