general waves

Question 1

what do waves do

Answer 1

transfer energy without transferring matter

Question 2

what is frequency

Answer 2

number of wavelengths passing a given point per unit time

Question 3

what is a wave period

Answer 3

the time for one oscillation

Question 4

define wavelength

Answer 4

the distance between identical points with the same phase

Question 5

what is the phase of a wave

Answer 5

describes how far through a cycle the wave is.

Question 6

what is the phase difference

Answer 6

phase difference measures the difference between where two waves are in the cycle. it can be measured as an angle or a fraction of the wavelength

Question 7

what is a transverse wave

Answer 7

the particles oscillate perpendicular to the direction of energy transfer

Question 8

what is a longitudinal wave

Answer 8

the particles oscillate parallel to the direction of energy transfer

Question 9

electromagnetic waves information

Answer 9

all are transverse,
all travel 3*10^8 m/s in a vacuum,
electric+magnetic fields oscillate perpendicular to the energy propagation

Question 10

define amplitude

Answer 10

the maximum displacement from the equilibrium position

Question 11

what is polarisation

Answer 11

when the oscillation of a wave is restricted to one plane. must be a transverse wave. oscillations must be perpendicular to the direction of energy transfer

Question 12

what is a polariser

Answer 12

a material that limits the plane of oscillation

Question 13

how does a polaroid material work

Answer 13

the molecules form parallel lines uniformly spaced
Any polarisation direction that is parallel to the molecules is absorbed,
Any polarisation direction that is perpendicular to the molecules is transmitted,
The transmitted light is at a lower intensity

Question 14

what happens to unpolarised light when reflected

Answer 14

when reflected from a transparent surface light becomes partially polarised parallel to the surface

Question 15

what would happen if two polarisers were placed next to each other with a 90° difference in orientation

Answer 15

no light could get through. the first one only transmits horizontally polarised light and the second would be vertically polarised only. so no light could get through both. (or the other way around)

Question 16

how are television/radio aerials oriented

Answer 16

they can be oriented so the spokes are horizontal or vertical. if a transmitter is sending out vertically polarised waves then the spokes should be vertical for maximum absorption of the waves for a good signal.

Question 17

how is a stationary wave formed

Answer 17

when two progressive coherent waves are moving in opposite directions and interfere with each other.

Question 18

what is a node

Answer 18

points on a standing wave of destructive interference

Question 19

whats an antinode

Answer 19

points on a standing wave of constructive interference

Question 20

whats a resonant frequency

Answer 20

frequencies that can form stationary waves.

Question 21

what are harmonics

Answer 21

resonant frequencies. they can form stationary waves. they are integer multiple of 1/2λ plus the fundamental frequency

Question 22

relationship between string length and frequency

Answer 22

long string length causes smaller frequency. because longer length causes a longer half-wavelength so there’s a lower frequency

Question 23

relationship between mass per unit length and frequency

Answer 23

greater mass per unit length = smaller frequency. because waves travel slower through a heavier string so the frequency will be lower if the string is a constant length

Question 24

relationship between tension and frequency

Answer 24

higher tension = higher frequency. because waves travel more quickly through a string with higher tension

Question 25

why does the soundhole in a guitar increase the pitch

Answer 25

The soundhole allows more air to be adjacent to the string while forming a resonant cavity which amplifies the sound waves

Question 26

what two properties of a wave are directly proportional

Answer 26

amplitude^2 and intensity

Question 27

define progressive wave

Answer 27

waves that transfer energy from one place to another but do not transfer matter

Question 28

define wave speed

Answer 28

the distance travelled by a wave per unit time

Question 29

define intensity

Answer 29

the power passing through a surface per unit area

Question 30

range of wavelengths of visible light

Answer 30

450-700nm

Question 31

why can x-rays and gamma rays have an overlap in there possible wavelengths

Answer 31

EM waves are defined by there sources not there wavelengths