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Physics > paper 2 : waves > Flashcards

paper 2 : waves Flashcards

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1
Q

what does a wave transfer

A

waves transfer energy without transferring matter

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2
Q

what are the 2 types of waves

A

the 2 types of waves are:

  • longitudinal
  • transverse
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3
Q

give some examples of longitudinal and transverse waves

A

some examples of longitudinal and transverse waves are :

  • longitudinal = sound and seismic push waves
  • transverse waves = all electromagnetic waves and seismic shake waves
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4
Q

what is meant by the ‘frequency’ of a wave

A

the frequency of a wave is the number of waves passing a point each second

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5
Q

how can you calculate the frequency of a wave

A

you can calculate the frequency of a wave by using this equation :
period = 1/frequency

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6
Q

what is frequency measured in

A

frequency is measured in hertz, Hz

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7
Q

what is meant by ‘period’

A

a period is simply the time taken to complete 1 complete wave

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8
Q

what is the speed of sound in air

A

the speed of sound in air is 334m/s

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9
Q

what is the speed of light and all electromagnetic waves

A

the speed of light and all electromagnetic waves is 3x 10^8 m/s

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10
Q

what happens to wave speed in a constant medium

A

in a constant medium(the same substance), wave speed stays the same

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11
Q

what is the range for normal human hearing

A

the range for normal human hearing is 20Hz to 20KHz

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12
Q

why are there restrictions to human hearing

A

there are restrictions to human hearing as the conversion of sound waves to vibrations of the solid, works over a limited frequency range

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13
Q

describe the effect of sound waves on the ear drum

A

sound waves affect the ear drum by:

  • differing pressures outside and inside the ear drum causes the ear drum to move
  • the differing pressures are caused by the compressions and rare-fractions of longitudinal sound waves on the outside of the ear
  • if the pressure is increasing, force in the ear must also increase as pressure is ∝ to force (F=pxA)
  • as the area inside and outside the ear is the same, a greater force on the outside of the ear compared to the one in the ear, will cause the ear drum to move inwards and vice versa
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14
Q

what are rare-fractions

A

rare-fractions are when the waves are furthest apart

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15
Q

what is the angle of incidence

A

the angle of incidence is the angle at which the ray reflects at

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16
Q

what can happen when a wave passes through a boundary(the end of a material and the start of a new one)

A

at a boundary waves can be either :

  • reflected
  • absorbed
  • transmitted without refraction
  • transmitted with refraction
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17
Q

what is refraction

A

refraction is when light rays bend towards the normal when they enter a new material

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18
Q

how can ultrasounds be used for medical imagery

A

ultrasounds are used for medical imagery as :

  • at the boundary between 2 different media (air and skin), the ultrasound waves are partially reflected
  • doctors can then determine how far away each boundary is by recording the time taken for the reflections to reach the detector
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19
Q

what are 2 uses of ultrasounds

A

2 uses of ultrasounds are :

  • unborn baby scans
  • measuring the speed of blood flow in a vein or artery
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20
Q

why is a gel used in baby ultrasounds

A

a gel used in baby ultrasounds as it prevents from all the waves being reflected: the gel balances the difference between the 2 medias

21
Q

list the types of electromagnetic waves in order of wave length (biggest to smallest)

A

the types of electromagnetic waves in order of wave length (biggest to smallest) are :

  • radio waves
  • microwaves
  • infrared
  • visible
  • ultraviolet
  • X-rays
  • gamma
22
Q

list the types of electromagnetic waves in order of frequency (smallest to biggest)

A

the types of electromagnetic waves in order of frequency (smallest to biggest) are :

  • radio waves
  • microwaves
  • infrared
  • visible
  • ultraviolet
  • X-rays
  • gamma -
23
Q

how does the speed of a wave change if was to enter a block

A

the speed of a wave in the block would be slower than the speed of the wave in air

24
Q

what is the principal focus (F on a ray diagram)

A

the principal focus is where all the fays of light are brought to focus

25
Q

what is the focal length

A

the focal length is the distance between the lens and the principal focus

26
Q

what do concave and convex lens’ do to light rays

A

concave lens cause light rays to diverge

convex lens cause light rays to converge

27
Q

what type of image will a concave or a convex lens produce

A

a concave lens will always produce a virtual image

a convex lens will always create a virtual or real image

28
Q

what is specular reflection

A

specular reflection is when reflection occurs from a smooth surface in one direction

29
Q

what is diffuse reflection

A

diffuse reflection is when reflection on a rough surface causes scattering

30
Q

how do colour filters work

A

colour filters work by absorbing certain wave lengths and colours and transmitting others

31
Q

what colour will an object be if all wave lengths are either :

  • absorbed
  • reflected
A

if all wave lengths are either absorbed or reflected the object will be :

  • black, if all waves are absorbed
  • white, if all waves are reflected
32
Q

what is the visible light spectrum

A

ROYGBIV = red, orange.yellow,green,indigo and violet

33
Q

what is an induced magnet

A

an induced magnet is a material that only becomes a magnet when places in a magnetic field BUT once it leaves that field it is no longer a magnet

34
Q

what type of force does induced magnetism always causes

A

induced magnetism always causes a force of ATTRACTION

35
Q

what is a magnetic field

A

a magnetic field is the region around a magnet where a force can act on another magnet or magnetic material

36
Q

what is a meant by ‘a perfect black body’

A

‘a perfect black body’ means that an object absorbs all the radiation incident on it(landing on it)
perfect black bodies don’ transmit or reflect any radiation

37
Q

how does the rate of emission and absorption affect temperature

A

the rate of emission and absorption affect temperature as :

  • a body will be at a constant temperature if the rate of absorption and emission are euqal
  • the body’s temperature will increase if rate of absorption is higher and the body’s temperature will decrease if the rate of emission is higher
38
Q

what happens when a current flows through a conducting wire

A

when a current flows through a conducting wire , a magnetic field is produced around that wire

39
Q

how can the the strength of a magnetic field created by current running through a wire be increased

A

the the strength of a magnetic field created by current running through a wire be increased by :
-shaping the wire into a solenoid

40
Q

what is the motor effect

A

the motor effect is when a conductor carrying a current is placed in a magnetic field causing the magnet producing the field and the conductor to exert a force on each other

41
Q

how can flemmings left hand rule be used to find out the direction of the force

A

flemmings left hand rule be used to find out the direction of the force as :

  • your thumb = the force
  • index finger = direction of magnetic field
  • middle finger = direction of current
42
Q

how can the direction of the force be reversed

A

the direction of the force be reversed by reversing the :

  • current
  • magnetic field
43
Q

what factors affect the magnitude of the force

A

factors which affect the magnitude of the force are :

  • the strength of the magnetic field
  • the amount of electrical current flowing through the wire
  • length of wire in the magnetic field
44
Q

what is magnetic flux density (strength of field) measured in

A

magnetic flux density (strength of field) is measured in tesla,T

45
Q

what is the generator effect

A

the generator effect is the induction of a potential difference(and current if the circuit is complete) in a wire which is experiencing a change in magnetic field

46
Q

how can you increase the induced potential difference (generator effect)

A

you increase the induced potential difference by :

  • increasing the strength of the magnet
  • increase the force(move the wire quicker)
  • increase the length of the wire in the field
47
Q

how can the induced p.d be reversed

A

the induced p.d be reversed by :

  • reversing the poles of the magnet
  • reversing the force direction
48
Q

how does a microphone work

A

a microphone works as :

  • sound energy enters the dust cover and there are alternating periods of high and low pressure(the compressions and rare-fractions of the waves)
  • so the resultant force is always changing direction due to at high pressures the force is high and at low pressures the force is low
  • one side of the diaphragm has constant pressure but on the other side its always changing causing the diaphragm to move in and out
  • diaphragm moves in, it cuts the magnetic filed, causing coil to cut the magnetic field and induce a p.d
  • if the circuit = complete a current flows
49
Q

explain how an alternating current in one coil induces a current in another (transformers)

A

an alternating current in one coil induces a current in another as :

  • the alternating p.d is applied to the primary coil
  • an alternating current on the primary coil occurs
  • the alternating current in the primary coil produces a changing magnetic field around the primary coil
  • the changing magnetic field gets trapped in the iron core
  • the changing magnetic field cuts across the secondary coil
  • a p.d is induced in the secondary coil and if it is in a complete circuit an alternating current is produced

Physics (6 decks)

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