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Physics YEAR 1 and 2 > WAVES > Flashcards

WAVES Flashcards

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1
Q

what two forms can waves take?

A

Longitudinal and transverse

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2
Q

what is longitudinal waves

A

waves which, the oscillations are parallel to the direction of travel

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3
Q

what is a transverse wave

A

a wave which will oscillate perpendicular to the direction of travel

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4
Q

what are progressive waves

A

waves which transfer energy from a source

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5
Q

what is phase difference

A

two points have exactly the same pattern of oscillation are said to be in phase.

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6
Q

how do you use an oscilloscope to find the frequency of a wave

A

-displays a voltage-time signal, can measure the from a signal generator, representing displacement over time.

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7
Q

how do you work out the speed of a wave?

A

v=fλ

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8
Q

calculate intensity

A

intensity= power/area

power= energy/time

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9
Q

calculate intensity if power spreads out in all directions

A

power/ 4πr^2

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10
Q

define intensity

A

that rate at which energy is transferred from one location to another as the wave travels through space.

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11
Q

what is the relationship between intensity and amplitude

A

I=a^2

because the amplitude of a wave decreases as it moves away from a source.

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12
Q

what is refraction

A

occurs when a wave moves from one medium to another, when they have different densities. the wave will change speed and maybe direction

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13
Q

define diffraction

A

is the spreading out of a wave after passing around an obstacle or through a gap

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14
Q

define interference

A

is the addition of two or more waves (superposition) that results in a new wave pattern

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15
Q

what are properties of em waves

A

-travel through vacuum
-travel at speed of light in vacuum
-can be polarised
-demonstrate interference

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16
Q

what is the λ of radio

A

10^-1 to 10^4

17
Q

what is the λ of microwave

A

10^-4 to 10^-1

18
Q

what is polarisation

A

when the oscillations of the field and direction are confined to a singular plane

19
Q

how can we observe the polarisation of microwaves

A

wave transmitter- transmits unpolarised waves
place metal grill in front of wave, with horizontal grills
microwave receiver picks up signal- connected to ammeter

20
Q

what is malus law

A

when you have two polarising filters, when you rotate the second one at an angle of ø to the first, the amplitude will be Acosø.

21
Q

what is a refractive index

A

a way to measure how the speed of a wave will change when entering a material of different density.
the speed will decrease as it enters from lower refractive index to higher index

22
Q

calculate refractive index

A

n=c/c in the material

23
Q

what is snells law

A

n1 x sinø1=n2 x sinø2

or nsinø=constant

24
Q

what is the diffraction grating equation

A

n lamda=dsinø
n is the order
ø is the angle to the order n

25
Q

what is total internal reflection

A

is the result of both reflection and refraction. we observe it when light travels from a material of higher to lower refractive index. Initially at an angle lower than the critical angle refraction will occur and there will be weak reflected ray

26
Q

what is the critical angle

A

the greatest angle at which a ray of light, travelling in one transparent medium, can strike the boundary between that medium and a second of lower refractive index without being totally reflected within the first medium.

27
Q

calculate the critical angle

A

sinC=1/n1

C is the critical angle
n1 is the material of higher refractive index

28
Q

if intensity increases by a factor of 2, what does amplitude increase by?

A

root 2

29
Q

if an amplitude increases by two, what does the area underneath increase by?

A

4

30
Q

what is the relationship between amplitude and intensity

A

a ^2 prop I

31
Q

what is the refractive index

A

the ratio of the speed of light in a vacuum to the speed of light in the material

32
Q

how do you calculate the amplitude of a wave passing through an angle of polaroid

A

A=AoCosø

33
Q

equation for microwave intensity passing through metal bars in relation to angle

A

IoCos^2ø=I

34
Q

what is snells law (air)

A

sin i/sin r =n of denser material

Physics YEAR 1 and 2 (24 decks)

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