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Higher Physics - 2021/2022 > Particles & Waves Sub Unit Test > Flashcards

Particles & Waves Sub Unit Test Flashcards

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1
Q

What is interference?

A

Occurs when waves from two or more sources meet

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2
Q

What is the resultant wave from inference determined by?

A

The amplitude and relative phase of the waves

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3
Q

What happens when two wave meet in phase?

A

Constructive interference

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4
Q

What does ‘in phase’ mean?

A

When the crests meet the crests and the troughs meet the troughs of another wave

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5
Q

What happens when waves are constructive?

A

Form a singular wave of greater amplitude

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6
Q

What happens when two waves out of phase meet?

A

Destructive interference

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7
Q

What does ‘out of phase’ mean?

A

When crest meets trough

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8
Q

What happens when waves are destructive?

A

The waves cancel each other out

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9
Q

What does it mean for waves to be coherent?

A

Same frequency
Same wavelength
Same velocity

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10
Q

What is a maxima?

A

Maxima are regions where two waves meet in phase and interfere constructively.
In terms of speakers, these are loud regions
In terms of light, these are the bright points

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11
Q

What is a minima?

A

Regions where two waves meet out of phase and interfere destructively.
In terms of speakers, these are the quiet regions
In terms of light, these are the dull/blank regions

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12
Q

What is path difference?

A

The extra distance travelled by one wave source compared to another source

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13
Q

How do you work out the path difference for constructive interference?

A

p.d. = m x wavelength

where m = 0,1,2 (which is what point it is)

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14
Q

How do you work out the path difference for destructive waves?

A

p.d. = (m + 1/2) x wavelength

where m = 0,1,2, 3

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15
Q

How would you work out the wavelength of something when given the distance between two speakers and the maxima/minima?

A

Work out p.d. by distS2p -distS1p
Sub into p.d. = m x wavelength
Rearrange to find wavelength

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16
Q

What is Young’s double slit experiment?

A

Passes light through a narrow slit then using two slits to divide the waves which produces bright and dark fringes on a screen

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17
Q

In diffraction, what happens to the fringes when the distance between the two slits (2) increases?

A

Fringes are closer together

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18
Q

What happens when the distance (D) between the slits and the screen increases?

A

The distance between the fringes increases

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19
Q

What is a diffraction grating?

A

A series of narrow parallel slits etched onto glass

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20
Q

What happens when the number of slits on a diffraction grating increase?

A

A series of bright sharp lines are produced

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21
Q

What does m=0 mean?

A

There is no path difference

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22
Q

What does m=1 mean?

A

There is a path difference is exactly on wavelength

pd = 1 x wavelength

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23
Q

If the diffraction grating is given in lines per mm, how would you find d?

A

Convert into metres by dividing by 1000

d = 1/no. of lines per metre

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24
Q

What happens when a wave moves from one medium to another?

A

Wave changes speed, can lead to a change in direction

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25
Q

What is the change of direction when a wave moves from one medium to another referred to as?

A

Refraction

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26
Q

What happens to the velocity, frequency and wavelength of a wave been it enters glass from air?

A

Velocity decreases
Frequency remains unchanged
Wavelength decreased

27
Q

When does the direction of a wave change in diffraction?

A

When it enters a medium at an angle

28
Q

What is the refractive index of a median?

A

A measure of how much the material changes the speed of light when it passes through it. Also a measure of the direction change

29
Q

What is the symbol for refractive index?

A

n

30
Q

What is the absolute refractive index in a vacuum and air?

A

1.00

31
Q

How would you calculate the refractive index?

A 
n = sin theta in air / sin theta in material
n = V in air / V in material
n = wavelength in air / wavelength in material
32
Q

What is the critical angle?

A

The angle of incidence for a material that results in an angle of refraction of 90 degrees

33
Q

What is total internal refraction?

A

When the angle of incidence is greater than the critical angle and all the light is reflected inside the material.

34
Q

What is a uses of internal reflection?

A

Optical fibres

35
Q

How would you calculate the critical angle?

A

sintheta = 1/n

where n=refractive index

36
Q

What is irradiance?

A

The power of radiation per unit area

37
Q

What is the symbol for Irradiance?

A

I

38
Q

What are the units for irradiance?

A

Wm-2

(Watts per metre squared

39
Q

What is the relationship between irradiance and distance?

A

As the distance from the source increases, the irradiance decreases

40
Q

What would a graph of distance against irradiance look like?

A

Same shape as a cooling curve

41
Q

What is the purpose of the inverse square law?

A

To prove that irradiance varies with the square of the distance from the source
i.e. doubling the distance results in a quartered irradiance

42
Q

Describe an experiment to verify the inverse square law of light.

A

Place a lamp at one end of a metre stick and a light intensity metre at the other end
Use the light detector to record intensity levels at different known distances from the lamp
Repeat the measurements

43
Q

Describe how apparatus could be used to verify the inverse square law for a point source of light.
(With the lamp, metre stick, and the light intensity metre)

A

Obtain values of irradiance for different distances
Plot graph of I against 1/d2 (1 divided by distance squared)
Graph of I against 1/d2 is a straight line through the origin to prove that it is constant

44
Q

What are the formulas to find irradiance?

A 
I = P/A
I = k / d2
I = 1 /d2
I1d1 = I2d2
45
Q

When are line spectra emmited?

A

When an electric current passes through a low pressure gas

46
Q

Why is spectra described as an atomic fingerprint?

A

Because each element has its own unique line spectrum

47
Q

How can line emission be observed?

A

With a spectrometer using a diffraction grating or a prism

48
Q

What can spectra be used for?

A

Identify elements present in distant stars and galaxies
Measure redshift of galaxies
Determine the rate of universal expansion

49
Q

What creates line spectra?

A

The transition of of electrons between energy levels

50
Q

How do absorption lines in sunlight spectrum allow us to determine the elements present in the suns atmosphere?

A

As light from hotter regions of the sun pass through cooler regions of the upper atmosphere, atoms absorb light at specific frequencies/wavelengths to produce an absorption spectra. These absorption lines allow the elements present to be identified.

51
Q

What is meant by continuous spectra?

A

Spectrum of light with no visible separate spectra lines

52
Q

How do electrons move between orbits?

A

Can adopt a new orbit level but cannot stop in between the electron levels

53
Q

What is the lowest energy level of electron orbiting called?

A

Ground state

54
Q

What is it called when an electron moves to a higher energy level?

A

It is in an excited state

55
Q

What does ionisation level mean?

A

That an electron has gained sufficient energy to escape from the atom completely

56
Q

When does an electron have zero energy?

A

When it has reached the ionisation level

57
Q

Why does an electron being ionised have zero energy?

A

Because electrons have a negative energy, so to get to zero requires a lot of energy

58
Q

When is delta E used?

A

When comparing energy levels in atoms

59
Q

When and where to electron transitions take place?

A 
Where = between the energy levels of an atom 
When = an electron either absorbs or emits a photon of electromagnetic radiation
60
Q

What does E=hf relate to?

A

The frequency of an emitted photon

where h is plancks constant

61
Q

What is the relationship between the jump in electron levels and the frequency of the photon emitted?

A

As the size of the jump increases, the frequency of the photon emitted also increases

62
Q

Describe how an electron can make the transition to a higher energy level.

A

By absorbing a photon of the electromagnetic radiation that had energy equal to precisely the difference between energy levels

63
Q

Describe the process of an electron moving from a higher energy level to a lower energy level.

A

The electron loses energy as it moves to a lower energy level and emits a photon in the process. The energy of the photon is equal to the difference between levels

Higher Physics - 2021/2022 (4 decks)

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