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waves Flashcards

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1
Q

progressive wave is
example?

A

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

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2
Q

transverse waves? e.g.?

A

oscillations are perpendicular to the direction of energy transfer
em waves

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3
Q

longitudinal waves
example

A

oscillations are parallel to the direction of energy transfer
sound

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4
Q

amplitude definition
wavelength definition

A

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

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5
Q

frequency definition

A

the number of wavelengths passing a given point per unit time

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6
Q

when is a wave in phase/antiphase

A

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

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7
Q

reflection definition
law of reflection

A

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

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8
Q

refraction definition
where will it refract towards the normal?

A

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

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9
Q

what does refraction have an affect on

A

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

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10
Q

diffraction definition
diffraction occurs the most when?

A

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

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11
Q

What is polarisation

A

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

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12
Q

Which waves can be plane polarised

A

Transverse
Longitudinal cannot as oscillations already limited to one plane

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13
Q

What does partial polarised mean
When does this happen?

A

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

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14
Q

What is the intensity of a wave
UNITS

A

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

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15
Q

How to calculate intensity
Intensity and amplitude relationship

A

POWER / Cross sectional area
Intensity directly proportional to amplitude squared

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16
Q

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

A

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)

17
Q

properties of em waves

A

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

18
Q

What is the relationship between rarefractive index and the normal

A

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

19
Q

What is total internal reflection

A

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

20
Q

What are the two condition required for total internal reflection

A
  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
21
Q

Angle of * at a * that produces

What is a critical angle

A

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

22
Q

what does superpose mean and principle of superposition

A

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

23
Q

difference between superposition and interference

A

interference is when the waves continuously pass through each other

24
Q

difference between constructive and destructive interference

A

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

25
Q

coherence definition

A

waves emitted from two sources that have a constant phase difference

26
Q

difference between path difference and phase difference

A

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

27
Q

describe youngs double slit experiment

A

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

28
Q

how is a stationary wave formed

A

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

29
Q

what is a node

A

a point on a wave with no displacement at all times

30
Q

what is an antinode

A

point on a wave that oscillates with maximum amplitude

31
Q

(in sound and microwaves)

where is the energy in stationary waves

A

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

32
Q

Fundamental wave (on a rope) properties

A

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

33
Q

Fundamental wave (1 end open) properties

A

1st harmonic
F0 frequency
Wavelength 4L
A
N

34
Q

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

A

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

35
Q

Fundamental wave (both ends open) properties

A

1st harmonic
F0
Wavelength 2L
A A
N

36
Q

How to test polarisation

A

2 polarising filters one horizontal one vertical should have 0 intensity

37
Q

Time period

A

time taken for one complete oscillation

38
Q

Polarisation of microwaves practical

A

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

physics (9 decks)

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