waves

Question 1

what is a particles rest position called

Answer 1

equilibrium position

Question 2

how do particles return to their equilibrium position in a wave

Answer 2

particles in the medium exert a force on each other. A displaced particle experiences a restoring force from its neighbour and it pulls it back to its og position

Question 3

transverse vs longitudinal

Answer 3

t- perpendicular to oscillation or energy transfer
l- parallel to oscillation or energy transfer

Question 4

how do longitudinal particles revert to their equilibrium position

Answer 4

displaced particles bounce off their neighbour providing the restoring force

Question 5

period

Answer 5

time taken for one oscillation

Question 6

frequency

Answer 6

number of complete wavelengths in one second

Question 7

how to calculate wave speed

Answer 7

frequency x wavelength

Question 8

how to find frequency from period

Answer 8

they are inversely proportional so f= 1/T

Question 9

what is a wave profile

Answer 9

a graph showing the displacement of the particles in a wave against the distance along the wave

Question 10

phase difference

Answer 10

How far out of step the oscillations of two points on the same wave are measured in degrees or radians

Question 11

what is in phase

Answer 11

if two particles reach max positive or max negative displacement at the same time

Question 12

what is anti phase

Answer 12

if one particles reach max positive while the other reaches max negative at the same time - completely out of phase represented as 180*

Question 13

snell law

Answer 13

sin i/sin r = n (n is refractive index)

Question 14

how is refractive index calculated

Answer 14

n= c/v ( c= speed of light through a vacuum and v= speed of light through material)

Question 15

what does a large refractive index entail

Answer 15

there the light entering is refracted towards the normal

Question 16

refractive law

Answer 16

n sin i = constant

Question 17

what does the refractive law entail

Answer 17

n1 sin 0 1 = n2 sin 02

Question 18

total internal reflection

Answer 18

occurs at the boundary between two different medians

Question 19

conditions for TIR

Answer 19

1. light must be traveling through a medium with a higher refractive index as it strikes the boundary with a medium with a lower refractive index
2. angle at which light strikes the boundary must be above critical angle

Question 20

how to work out critical angle

Answer 20

sin C = 1/n

Question 21

partially polarised

Answer 21

description of a transverse wave in which there are more oscillations in one particular plane, but the wave is not completely plane polarised- occurs when transverse waves reflect off a surface

Question 22

plane polarised

Answer 22

description of a transverse wave in which the oscillations are limited to only one plane

Question 23

unpolarised

Answer 23

description of a transverse wave in which oscillations occur in many planes

Question 24

relationship between intensity and amplitude

Answer 24

intensity is directly proportional to amplitude squared

Question 25

intensity formula

Answer 25

I = P/A intensity ( Wm^-2) = power (watts) / area (m^2)

Question 26

what does intensity formula represent

Answer 26

the amount of energy per unit area per unit time

Question 27

reasons for cladding

Answer 27

- protects the core from breakage - prevents crossover of signal when in contact with other fiber - increase rate of data transfer - reduces smearing

Question 28

sound quality of radio is improved when adjusting the orientation of aerial. why?

Answer 28

radio waves from transmitter are polarised.

Question 29

why is the speed of light increased in medians with a higher density

Answer 29

particles are closer together so stronger restoring force are passed more rapidly from one particle to the next

Question 30

in deep water does wave length increase or decrease and why

Answer 30

increases because wave speed increases and they are proportional as frequency is constant. wave speed increases because in deeper water, the wave is less affected by friction with the seafloor and has more available fluid to move with

Question 31

why is diffraction of sound regularly observed but not the diffraction of light

Answer 31

diffraction effects are most significant when the wavelength is similar to the gap. Light has a very small wavelength and is normally smaller than most gaps whereas sound has a much larger wavelength.

Question 32

why does maximum and minimum intensity occur in 90* increments when two polaroids are used

Answer 32

at 0,180 ans 360, polarises are aligned in the same plane so maximum intensity is received as 90 and 270, polaroids are aligned in opposite planes so intensity falls to 0.

Question 33

define a progressive wave

Answer 33

a transfer of energy as a result of an oscillation

Question 34

what is diffraction

Answer 34

wavefronts spread after passing through a gap or around an obstacle.

Question 35

how can you demonstrate sound diffracts using a loudspeaker and a sound wave with wl 0.10m

Answer 35

set up a barrier with a gap respective to the wavelength of the sound wave ( less than 0.1) then place an observer outside of the geometrical shadow region. If sound detected this shows diffraction

Question 36

phase difference equation

Answer 36

(wavelength/distance between the two point)s x360

Question 37

experiment to prove an angle of reflection causes a wave to become plane polarised using a polaroid.

Answer 37

Set up apparatus, e.g. tray of water on table with lamp/light from window rotate the filter rotation of filter changes the image intensity/brightness correct orientation for maximum and minimum intensities of image move head up or down to change angle of reflected light observed use of protractor to measure angles image/reflection becomes partially plane polarised/ image changes from bright to dim but does not disappear

Question 38

polarised wave

Answer 38

description of a transverse wave where its oscillations are restricted to one plane

Question 39

frequency of microwaves

Answer 39

~300 MHz to 300 GHz.

Question 40

length of visible light

Answer 40

400-700nm

Question 41

Effect on oscilloscope trace if time base is switched off

Answer 41

Vertical line is formed of equal length to twice the peak voltage because trace no longer moves horizontally

Question 42

Describe how the student produces Fig. 5.1 experimentally using a ray box.

Answer 42

Use a single slit / yellow filter (in the ray box) • Use of dim lighting / darkened room • Draw around the glass block • Use a protractor to measure 90° for the normal OR to measure angles • Draw crosses / use pins (a long way apart) on the incident ray / mark incident ray (with ruler) • Mark point Q • (Remove block and) then join P to marked point Q