11. waves

Question 1

progressive wave is
example?

Answer 1

oscillation that travels through matter
all transfer energy, but not matter
sound

Question 2

transverse waves? e.g.?

Answer 2

oscillations are perpendicular to the direction of energy transfer
em waves

Question 3

longitudinal waves
example

Answer 3

oscillations are parallel to the direction of energy transfer
sound

Question 4

amplitude definition
wavelength definition

Answer 4

maximum displacement from the equilibrium position
distance on a wave from peak to peak

Question 5

frequency definition

Answer 5

the number of wavelengths passing a given point per unit time

Question 6

when is a wave in phase/antiphase

Answer 6

in phase= particles oscillating perfectly in step with one another
antiphase= 180 degrees out of phase

Question 7

reflection definition
law of reflection

Answer 7

when a wave changes direction at a boundary between two different media
angle of incidence = angle of reflection

Question 8

refraction definition
where will it refract towards the normal?

Answer 8

when a wave changes direction as it changes speed (some reflection - partial reflection- will occur)
if it speeds up, it will refract towards the normal

Question 9

what does refraction have an affect on

Answer 9

the wavelength but not its frequency
wave slows down - wavelength decreases

Question 10

diffraction definition
diffraction occurs the most when?

Answer 10

when waves pass through a gap or travel round an object, they spread out

the size of the gap or obstacle is about the same as the wavelength of the wave

Question 11

What is polarisation

Answer 11

The particles oscillate in one direction only- the wave is confined to a single plane

Question 12

Which waves can be plane polarised

Answer 12

Transverse
Longitudinal cannot as oscillations already limited to one plane

Question 13

What does partial polarised mean
When does this happen?

Answer 13

There are more waves oscillating in one particular plane but the wave is not completely plane polarised
When waves reflect off a surface

Question 14

What is the intensity of a wave
UNITS

Answer 14

The radiant power passing through a surface per unit area
Wm-2

Question 15

How to calculate intensity
Intensity and amplitude relationship

Answer 15

POWER / Cross sectional area
Intensity directly proportional to amplitude squared

Question 16

order of the em spectrum (biggest wavelength to smallest wavelength)
Properties

Answer 16

1.Radiowaves 10’2low freq, high wavelength
2.Microwaves 10-2
3. Infra red 10-4
4. Visible light 400-700nm
5.Ultraviolet 10-8
6.X-rays 10-10
7. Gamma rays 10-12
High freq, low wavelength High E (dangerous)

Question 17

properties of em waves

Answer 17

Can be reflected, rarefracted and diffracted.
Can be plane polarised.
Travel at the same speed through a vacuum

Question 18

What is the relationship between rarefractive index and the normal

Answer 18

The higher the rarefactive index, the closer the refracted line to the normal

Question 19

What is total internal reflection

Answer 19

When light strikes a boundary and all the light is reflected back into the original medium

Question 20

What are the two condition required for total internal reflection

Answer 20

1. Light must be travelling from a medium with a higher refractive index into a medium with a lower refractive index.
   2.Angle that the light strikes the boundary must be above the critical angle

Question 21

Angle of * at a * that produces

What is a critical angle

Answer 21

The angle of incidence at a boundary between two different media that will produce an angle of refraction of 90 degrees

Question 22

what does superpose mean and principle of superposition

Answer 22

when waves overlap
When two waves meet at a point the resultant displacement at that point is equal to the sum of displacements of the individual points

Question 23

difference between superposition and interference

Answer 23

interference is when the waves continuously pass through each other

Question 24

difference between constructive and destructive interference

Answer 24

constructive is when the two waves are in phase
destructive is when the waves are in antiphase

Question 25

coherence definition

Answer 25

waves emitted from two sources that have a constant phase difference

Question 26

difference between path difference and phase difference

Answer 26

path difference to do with the distance travelled
phase distance to do with how out of sync the waves are - degrees

Question 27

describe youngs double slit experiment

Answer 27

Used a monochromatic source of light and a narrow slit to diffract the light.
Light diffracting from the single slit reaches the double slit in phase, which then diffracts again

Question 28

how is a stationary wave formed

Answer 28

when two progressive waves with same frequency and amplitude, moving in opposite directions superpose (which means overlap) to create nodes and antinodes which do not move

Question 29

what is a node

Answer 29

a point on a wave with no displacement at all times

Question 30

what is an antinode

Answer 30

point on a wave that oscillates with maximum amplitude

Question 31

(in sound and microwaves)

where is the energy in stationary waves

Answer 31

SOUND- silence at nodes, maximum volume at antinodes
MICROWAVE - no heating at nodes maximum heating at antinodes

Question 32

Fundamental wave (on a rope) properties

Answer 32

1st Harmonic
F0 frequency
Wavelength 2L
A
N. N

Question 33

Fundamental wave (1 end open) properties

Answer 33

1st harmonic
F0 frequency
Wavelength 4L
A
N

Question 34

How do the harmonics on a wave 1 end open differ from harmonics of wave on a rope

Answer 34

Harmonics wave on a rope increase by 1
Harmonica 1 end open only have odd harmonics

Question 35

Fundamental wave (both ends open) properties

Answer 35

1st harmonic
F0
Wavelength 2L
A A
N

Question 36

How to test polarisation

Answer 36

2 polarising filters one horizontal one vertical should have 0 intensity

Question 37

Time period

Answer 37

time taken for one complete oscillation

Question 38

Polarisation of microwaves practical

Answer 38

Place a metal grille in between a microwave receiver and a microwave transmitter. Slowly rotate the grille. Voltage across receiver will be ,maximum when the microwaves pass through the grille