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Applied Science > Phy Unit 1 > Flashcards

Phy Unit 1 Flashcards

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1
Q

Milli

A

m
10-3

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2
Q

Micro

A

Ų
10-6

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3
Q

Nano

A

n
10-9

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4
Q

Kilo

A

K
10^3

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5
Q

Mega

A

M
10^6

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6
Q

Giga

A

G
10^9

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7
Q

T = 1/f

A

T - time period
f - frequency

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8
Q

Displacement-time graph

A
  • graph of oscillations
  • displacement plotted against time
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9
Q

What is the use of a distance-time graph?

A

Amplitude, period and frequency of an oscillating object

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10
Q

Finding amplitude on D-T graph

A

No negative value
Amplitude - maximum displacement measured from the central resting point

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11
Q

Finding period on D-T graph

A

Period- the amount of time it takes for one complete oscillation

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12
Q

Wavelength

A

The distance between two Crests or trough

On longitudinal wave its the compression or rarefraction

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13
Q

v= f λ

A

Speed of the wave

v- speed m/s
λ- wavelength m
f- frequency Hz

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14
Q

Oscillations

A

a regularly repeating motion about a central value.

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15
Q

Frequency

A

Number of complete oscillations to occur per sec
Hertz Hz

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16
Q

Displacement

A

How far from the equilibrium point the wave have oscillatated

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17
Q

Phase difference

A

Aka oscillations out of phase
- a fraction of a cycle by which one particle oscillates behind another particle

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18
Q

Wave types

A
  • longitudinal
  • transverse
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19
Q

Transverse waves

A

Oscillations are perpendicular to the direction of energy transfer

  • electromagnetic eg light & radio waves
    -wave of string
    -ripples/waves
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20
Q

Longitudinal waves

A

Oscillations are parallel to the direction of energy transfer
Compression and rarefractions

  • sound waves
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21
Q

Wave facts

A
  • energy is transferred from one place to another
  • no transfer of matter
  • Displacement is a vector
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22
Q

What are compressions ?

A

Region of particles that are closer together

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23
Q

What are rarefractions?

A

Particles are further apart/ spread out

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24
Q

WS in stringed musical instruments

A
  • tune wivout changing length as you change the medium and altering the speed of waves
25
Q

WS types of strings

A

Thicker- more mass is per unit length, ų, gives a slower speed = lower note

Tighter- more tension (T), faster speed = higher note.
Tension is measured in newtons (N)

26
Q

WS in MS equation

A

v = √ (T/v)

27
Q

WS air column in pipes

A

The speed of sound is fixed given any temp or pressure. Only tune by altering the length of brass or woodwind instruments

28
Q

MI per unit length

A

Ų (= m/L)

29
Q

Refraction

A

Occurs when wave changes it’s direction and speed as it passes from one medium to another

30
Q

Refractive index

A

The ratio of the speed of light in a vacuum divided the speed of light in a medium

n= c/v

31
Q

n= c/v = sin i/ sin r

A

Refractive index

n = RI
c- speed of light in vacuum
(3.0 x 10^8 m/s-1)
V- speed of light in the medium

i- angle of incident
r- angle of reflection
Delta y / D x = gradient

32
Q

Higher RI =

A

More refraction taking place
More dense the material

33
Q

Total internal reflection

A

As the light hit the boundary between glass and air = refract

  • material of high RI to a lower RI the light bends away from the normal
  • as we increase angle of incidence the angle of refraction also increases
34
Q

Critical angle

A

The ray will fully remain in the og medium

1/n = v/c = sin c

35
Q

When does TIR occur

A

It occurs when the angle of incidence is higher than the critical angle.
The ray will remain in the original medium.

36
Q

Coherent

A

Same frequency and fixed phase relationship

37
Q

Principle of superposition

A

Waves from different sources cross and their amplitudes add together

38
Q

Constructive

A

Waves arrive in phase= double amp large amplitude signal

39
Q

Destructive

A

Waves arrive in anti-phase = 0 amp
Small amplitude Signal

40
Q

Path difference in WI

A

A full number of wavelengths = constructive

An odd number of half wavelengths = destructive

41
Q

Grating

A

flat arrays of regularly spaced lines, which are designed to break up a plane wave-front into a set of separate wave sources.

42
Q

Path difference—> phase difference

A

a path difference is created by dividing a light source so that separate rays of light travel different paths = phase difference

the path difference increases as the angle through which a grating scatters the light is increased

= a whole No of WL nħ LR are in phase = bright fringe

= • in between, at a path difference of ħ/2, 3ħ/2, …, destructive interference gives a dark fringe.

43
Q

Purpose of Path difference—> phase difference

A

Produce dark and bright interference fringes

44
Q

Spectra

A

When light has a mixture of wavelengths, constructive interference occurs at different angles for each wavelength = a set of coloured line spectra is produced rather than just a set of bright fringes.

45
Q

Emission spectra

A

The light emitted when the electrons in atoms are excited by heating or by an electric discharge is characteristic of the electronic structure of the element(s) present.

46
Q

What experiment is used for ES

A

Flame tests use this idea to identify elements.

Elements such as heavy metals can be vapourised.

permanent gases such as neon are used in electric discharge lamps to give characteristic coloured light outputs.

47
Q

Stationary waves

A

Stationary waves can be thought of as two progressive (travelling) waves moving in opposite directions and superimposed one on the
other.

The result is a fixed pattern of nodes and antinodes.

48
Q

Nodes

A

Nodes have minimum (ideally zero) oscillation

49
Q

Antinodes

A

antinodes are points of maximum amplitude.

50
Q

Resonator

A

store wave energy by reflecting the wave back on itself to form a stationary wave pattern

51
Q

Resonance

A

only efficiently receive energy from an external source that has a frequency close to one of their own natural frequencies

52
Q

Optical fibre

A

An optical fibre is a thin strand of high-quality glass. Light can be transmitted through it over very large distances. The optical fibre makes use of the ‘total internal reflection’ of light.

53
Q

What happens in optical fibre

A

Light from a range of angles is refracted on entering the cut end of a fibre so that it hits its inside surfaces at angles greater than the critical angle, C, and so is totally internally reflected. (Cladding has a lower value of n compared with the fibre core.)

54
Q

OF vs copper wire

A

because optical fibre signals:
• have lower losses, so travel further before needing amplification
• cannot be tapped into, so are secure
• carry higher frequencies, so provide greater bandwidth.

But optical fibres cost more and need specialist installation.

55
Q

Endoscopy

A

1 illumination
2 forming an image
3 analogue images

56
Q

Illumination

A

A small fibre bundle is used for piping light from an external source down to the distal (remote) end, where it illuminates the area being investigated.

57
Q

Forming an image

A

Lenses are used at both ends:

• A tiny objective lens at the distal end of an endoscope focuses an image onto cut ends of optical fibres in a second large bundle - the main bundle.

• Each fibre in the main bundle collects and carries the light for one pixel (coloured dot) the image.

• An eyepiece lens at the operator end takes light exiting from the fibre bundle and refocuses it to be viewed as an image directly by eye or with a camera

58
Q

Analogue image

A

Even though divided into pixels, these imag analogue - that is, the brightness and colour of each pixel vary with time in direct proportion the light collected by the objective lense

59
Q

Other device

A

Fingerprinting for security e.g. getting into a mobile phone: Where fingerprint lines touch the glass, they alter the critical angle and hence the amount of light reflected back internally to a detector.

Applied Science (3 decks)

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