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physics > paper 1 overview > Flashcards

paper 1 overview Flashcards

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1
Q

what is inertial mass

A

how difficult it is to change the velocity of an object

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2
Q

relationship between braking distance and speed

A

they have a squared relationship (if speed doubles, braking distance increases by a factor of 2^2, if speed trebles braking distance increases by a factor of 3^2

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3
Q

what equation can be used to calculate braking distance

A

1/2 x m x v^2 = F x d

energy in car’s kinetic store = work done by the brakes

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4
Q

mnemonic for em spectrum

A 
(longest wavelength)
real - radio waves
money - microwaves
is - infrared radiation
visible - visible light
using - ultraviolet
x-ray - x-rays
goggles - gamma waves
(highest frequency)
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5
Q

define transverse waves + examples

A

oscillations perpendicular to direction of travel

all em waves, s-waves, water waves

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6
Q

define longitudinal waves + examples

A

vibrations parallel to direction of travel

sound waves, P-waves

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7
Q

how does the ear work

A

sound waves cause your eardrum to vibrate
the vibrations are passed onto ossicles and then to the cochlea
the cochlea turns the vibrations to electrical signals which are sent to the brain
the brain interprets the sound depending of the frequency and intensity of the wave

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8
Q

characteristics of ultrasound

A

they get partially reflected at boundaries, the time taken for a reflection to reach a detector can be used to determine distance

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9
Q

p-waves

A

longitudinal
travel through both solids and liquids
faster than s-waves

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10
Q

s-waves

A

transverse
only travel through Solids
slower than p-waves

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11
Q

radio waves

A

communications, satellite transmissions

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12
Q

microwaves

A

internal heating of body cells

satellite transmissions, communications

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13
Q

infrared

A

skin burns

optical fibres, tv remote controls

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14
Q

visible light

A

photography, vision

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15
Q

ultraviolet

A

damage to surface cells and eyes –> skin cancer + eye conditions
disinfecting water, security marking

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16
Q

x-rays

A

mutation/damage to body cells

medical x-rays, airport security scanners

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17
Q

gamma rays (em)

A

mutation/damage to body cells

sterilising medical equipment/food, detecting and treating cancer

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18
Q

what is the law of reflection

A

angle of incidence = angle of reflection

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19
Q

when can total internal reflection occur

A

when the wave travels from a dense material into a less dense material

the angle of incidence has to be larger than the critical angle for this boundary between materials

if it is less than the critical angle/equal there is still some internal reflection

20
Q

primary colours of light

A

pure red, green and blue

21
Q

how do colour filters work

A

they only transmit certain colours of light and let them reach our eyes, the rest are absorbed

22
Q

principle focus of a diverging lens

A

the point where rays hitting the lens parallel to the axis appear to come from

23
Q

how is power affected by lens shape

A

converging lens - positive power
diverging lens - negative power
more curved = stronger power
a different material can be thinner but still better at focusing light

24
Q

use of focal distance in ray diagrams for converging vs diverging lenses

A

converging - from lens TO focal distance

diverging - from focal distance to lens (and continued)

25
Q

is there more danger with high or low frequency em waves

A

high frequency!

26
Q

how can electrons change energy levels

A

absorbing em radiation can cause an electron to rise to a higher energy level
the electron then falls back down to a lower energy level and the excess energy is carried away by em radiation

27
Q

alpha particles

A

helium nuclei - 2neutrons and 2protons
weakly penetrating - few cm in air, stopped by a sheet of paper
strongly ionising (bc of their size)

28
Q

beta particles

A

beta-minus particle - fast moving electron, a neutron changes into a proton and an electron
beta-plus particle - fast moving positron (electrons’s anti-particle)
both are moderately ionising

ß- - range of a few metres in air, absorbed by a 5mm thick sheet of aluminium
ß+ - smaller range bc when it meets an electron, the two destroy each other and produce gamma rays (PET scanning )

29
Q

gamma rays

how penetrating/ionising

A

travel v far in air, stopped by thick sheets of lead/ metres of concrete
weakly ionising bc they pass through atoms vs collide with them

30
Q

irradiation

A

when something is simply exposed to radiation (we are constantly irradiated by background radiation sources)

31
Q

how is radioactive contamination reduced

A

gloves and tongs - stop particles getting stuck to your skin/nails
protective suits - stop you breathing in particles

the danger is the decaying of the particles

32
Q

which radiation sources are most dangerous inside vs outside of the body

A

inside - alpha, strongly ionising so they do all their damage in a very localised area
outside - beta+gamma, they can penetrate the body and reach delicate organs but alpha can’t penetrate the skin

33
Q

how does photographic film detect radiation

A

the more radiation it’s exposed to, the darker it becomes

34
Q

radiation in fire alarms

A

weak alpha source in the smoke detector close to two electrodes
source causes ionisation and a current flows
fire? smoke absorbs charged particles, current stops, alarm sounds

35
Q

sterilising food and equipment

A

food can be irradiated with a high dose of gamma rays - killing all microbes, so food takes longer to go bad

same with medical equipment
good because doesn’t need high temps (unlike boiling)

36
Q

PET scanning

A

inject patient with a substance used by the body (eg. glucose), containing a ß+ emitting isotope with a short half life
also, the distribution of radioactivity matches with metabolic activity

37
Q

what radiation is used near tumors in implants

A

beta bc it can penetrate the casing of the implant (alpha is just injected nearby)

38
Q

chain reaction in nuclear fission

A
  • slow moving neutron fired at a large, unstable nucleus (usually uranium-235)
  • the neutron is absorbed and makes the nucleus more unstable so it splits
  • the split causes two new lighter elements, daughter nuclei, to form and energy is released as well as 2/3 neutrons
  • all of the new nuclei formed are radioactive and the neutrons spat out can go on to hit other uranium-235s
39
Q

controlling chain reactions

A 
uranium fuel rods are placed in a moderator to slow down fast moving electrons
control rods (often boron) limit fission rate by absorbing excess neutrons - they are placed between fuel rods and can be lowered and raised
40
Q

nuclear power stations

A
  • energy released by fission is transferred to the moderators thermal energy store
  • this transfers to the coolants thermal store
  • then to the thermal store of cold water passing through the boiler
  • this causes the water to boil, the energy transfers to the steam’s thermal store
  • energy transferred to kinetic store of turbine and then to ke of a generator
  • energy is transferred away from the generator electrically
41
Q

nuclear fusion

A

two lighter nuclei fuse to form one heavier nucleus + some energy released as radiation

can only happen at VERY high temperatures and pressures because the positively charged nuclei have to get very close to fuse and the strong force due to electrostatic repulsion has to be overcome

there are a few experimental fusion reactors rn but none are yet generating electricity

42
Q

steady state theory

A

universe has always existed it currently is and always will
as it expands, new matter is constantly created
the density is always roughly the same
no beginning/end to the universe
supported by red-shift

43
Q

Big Bang theory

A

initially all the matter in the universe else was compacted small, so it was very hot
it then ‘exploded’, space started expanding and is still going
gives a finite age for the universe
supported by both red-shift and CMB radiation

44
Q

stages of stars a similar size to the sun

A 
nebula
protostar
main sequence star
red giant 
white dwarf

no people, man Rawr went!

45
Q

describe the life cycle of stars of a similar size to the sun

A
  • initially forms from a cloud of dust and gas (nebula)
  • gravity pulls this together to from a protostar, star gets denser and more collisions so temp increases. eventually nuclear fusion keeps the core v hot and a star is born
  • the star enters a long stable period, here the outward pressure from thermal expansion balances gravity pulling things inward. its a main sequence star and lasts billions of years
  • eventually hydrogen in core starts running out and gravity>thermal expansion the star is compressed until it’s dense and hot enough that the energy created makes the outer layers expand and becomes a red giant (the surface cooling makes it red)
  • it then becomes unstable and ejects it’s outer layer of dust and gas, leaving behind a hot, dense solid core. a white dwarf.
46
Q

different types of telescopes

A

optical telescopes - only uses visible light
X-ray telescopes - can see high temp events, eg. exploding stars
radio telescopes - responsible for discovering CMBR

47
Q

modern telescopes

A

bigger telescopes = better resolution and able to gather more light, so we can see things that we couldn’t see before bc they were too faint
improved magnification = we can look further into space, more galaxies are being discovered

modern telescopes work with computers, creating sharper images that can easily be captured for later analysis - we can also use computers to store hugs amounts of data at any time, easy peasily

physics (6 decks)

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