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Unit 1 BTEC science > physics > Flashcards

physics Flashcards

1
Q

what is a transverse wave

A

particles that oscillate perpendicular to the direction of the wave. There is no horizontal movement.

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2
Q

what is a longitudinal wave

A

particles that oscillate parallel to the direction of the wave. there is no vertical movement.

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3
Q

what is the peak

A

the point of maximum positive displacement

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4
Q

what is the trough

A

the point of maximum negative displacement

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5
Q

what is equilibrium

A

the point at which particles remain where there is no disturbance

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6
Q

what is the amplitude

A

the difference between the max and the equalibrium

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7
Q

what is the wavelength

A

one point of a wave to the identical point on the next wave

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8
Q

what are examples of transverse waves

A

EM waves
String waves
water waves
S waves

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9
Q

what are examples of longitudinal waves

A

sound

P waves

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10
Q

what is frequency

A

the number of waves passing a point per second

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11
Q

what is period

A

time taken to produce one complete wave

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12
Q

what is the formula for velocity/ wavespeed

A 
V= Fx Lamda 
wavespeed= frequency x wavelength
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13
Q

what is the EM spectrum in order from shortest wavelength to longest wavelength

A 
gamma ray
x ray
UV
visible light
infrared
microwave
radio
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14
Q

what is the formula for period

A

1/ frequency

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15
Q

when is there no phase difference

A

when 2 waves run along the same way at the same point will form one wave (they have the same peak and trough)

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16
Q

when is there a phase difference

A

the fraction of a complete cycle between 2 points on a wave

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17
Q

what is reflection

A

when waves hit a barrier/ boundary that they cant pass through, they are reflected.

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18
Q

what is superposition

A

when 2 or more waves overlap, the displacement at a point is equal to the sum of the individual displacements at the point

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19
Q

what is constructive inference

A

if both waves the same displacement/ in phase

wave 1+ 2= wave 3

20
Q

what is destructive inference

A

when waves are 180 degrees out of phase
if one wave has a positive displacement and the other has a negative
wave 1-2= wave 3

21
Q

what is a stationary wave

A

when 2 progressive waves of the same frequency travel in opposite directions, a stationary wave is produced

22
Q

what is an antinode

A

when the maximum displacement occurs

23
Q

what is a node

A

when no displacement occurs

24
Q

what is the EM spectrum from the longest wavelength to shortest

A 
radio wave
microwave
infrared
visible light
visible light
UV
x rays
gamma rays
25
Q

why are lasers used as a light source

A

MONOCHROMATIC- emitted with only one wavelength
COHERENT- all waves are either exactly in phase or display a constant phase difference
COLLIMATED- a narrow, approximately parallel beam

26
Q

what is refraction

A

the change of direction a light ray undergoes when it enters a medium with a different optical density

27
Q

what happens when a light ray enters a medium that is more optically dense

A

it slows down and bends towards the normal

28
Q

what happens when a light ray enters a medium that is less optically dense

A

it speeds up and bents away the normal

29
Q

what is the formula for incident ray and refracted ray

A

I1= R2

30
Q

what is the formula for refractive index

A

refractive index of a substance (n) = speed of light in the vacuum (c) / speed of light in a substance (v)
OR
sin R (angle of refraction)/ sin I (angle of incidence)

31
Q

what are optical fibres used for

A

used to send light signals from one place to another eg cable TV

32
Q

how do optical fibres work

A

light from a source is directed into a narrow glass fibre

the ray will undergo a series of total internal reflection each time it works

33
Q

what are the improvements made on the optical fibre

A

to wrap the core fibre in a material called cladding
the cladding protects the core from scratches/ moisture that may enable light to leak out
this allows info to be transmitted with a greater degree of security

34
Q

what other ways do we use optical fibres other than in communication

A

endoscopes contain 2 bundles of fibres, one is used to light the inside of the person while the other is used to bring back info

35
Q

what are the types of signal transmissions

A

analogue signal and digital signal

36
Q

what is an analogue signal

A

varies continuously in frequency and amplitude eg speech and FM radio

37
Q

what is a digital signal

A

has only 2 states (on and off)
it is transmitted as a series of electrical or optical pulses. eg electrical pluses in cables, infrared pulses in optical fibres

38
Q

what is an emission spectra

A

the range of frequencies of light emitted by an element
is produced by an element due to energy level changes of electrons
the electrons lose energy when returning to a lower energy level they emit light of a specific frequency

39
Q

what is the speed (in instruments)

A

velocity of a wave on a string= tension in the string/ the mass per unit length of a string

40
Q

what are the advantages of digital signals

A

they are less affected by noise and have less energy loss and can travel further

41
Q

what are microwaves used for

A

mobile phone networks because their high frequency gives greater bandwidth which allows large amounts of data to be transmitted

42
Q

why are microwaves good

A

there is little to no interference because they can be divided into separate channels

43
Q

what is the quality of a signal affected by

A

wet weather as microwaves are strongly absorbed by water

44
Q

what is satellite communication

A

the signals are high power and are transmitted over long distances
radio waves are reflected by the ionosphere and so it can be used for terrestrial communication

45
Q

what are infrared communications

A

used in low power devices such as remote controls
operates over a short distance and in line of sight
doesnt work well in bright sunlight

Unit 1 BTEC science (4 decks)

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