P6 - Waves

Question 1

Amplitude

Answer 1

maximum displacement of a point on the wave from its undisturbed position

Question 2

Wavelength

Answer 2

distance between the same point on two adjacent waves (e.g.from trough to trough)

Question 3

Frequency

Answer 3

number of complete waves passing a certain point per second.

Question 4

Period equation

Answer 4

T = 1 / f

Question 5

Transverse waves

Answer 5

the oscillations are perpendicular to the direction of energy transfer

Question 6

Longitudinal

Answer 6

the oscillations are parallel to the direction of energy transfer

Question 7

wave speed equation

Answer 7

Wave speed = Frequency x Wavelength

Question 8

Wave is absorbed by the second material

Answer 8

The wave transfers energy to the material’s energy stores. Often, the energy is transferred to a thermal energy store, which leads to heating.

Question 9

Wave is transmitted through the second material

Answer 9

The wave carries on travelling through the new material. This often leads to refraction.

Question 10

The wave is reflected

Answer 10

This is where the incoming ray is neither absorbed or transmitted, but instead is ‘sent back’ away from the second material.

Question 11

EM wavelengths

Answer 11

Radio waves - 1m - 10^4m
Micro waves - 10^-2m
Infra red - 10^-5m
Visible light - 10^-7m
Ultra violet - 10^-8m
X-rays - 10^-10m
Gamma rays - 10^-15m

Question 12

Refraction

Answer 12

when a wave crosses a boundary between two materials it changes speed. If the wave hits the boundary at an angle it changes direction. The wave bends towards the normal if it slows down and bends away from the normal if it speeds up. The wavelength of the wave changes when it is refracted, but the frequency stays the same.

Question 13

Microwaves - satellites

Answer 13

the signal from a transmitter is transmitted into space where it’s picked up by the satellites receiver dish orbiting above the Earth. the satellite transmits the signal back to earth in a different direction where it is received by a satellite dish on the ground. There is a slight time delay between the signal being sent and received because of the long distance the signal has to travel.

Question 14

Microwaves - microwave ovens

Answer 14

The microwaves need to be absorbed by water molecules in food. The microwaves penetrate up to a few centimeters into the food before absorbed and transferring the energy they are carrying to the water molecules, causing the water to heat up.

Question 15

Infra red

Answer 15

IR is given out by all objects. The hotter the object, the more IR radiation it gives out.

Question 16

Visible light - fibre optic

Answer 16

optical fibres are thin glass or plastic fibres that can carry data over long distances and pulses of visible light. The light rays are bounced back and forth until they reach the end of the fibre.

Question 17

Ultraviolet

Answer 17

Fluorescent lights generate UV radiation, which is absorbed and re-emitted as visible light by a layer of phosphorus on the inside of the bulb.

Question 18

X-rays and Gamma rays

Answer 18

x-rays easily pass through flesh but not so easily through denser material like bones or metal. So it’s the amount of radiation that’s absorbed that gives an x-ray image.

A gamma-emitting source is injected into the patient, and its progress is followed around the body. It can pass out through the body to be detected