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🌌 > Wrong Questions - P5 to P8 > Flashcards

Wrong Questions - P5 to P8 Flashcards

1
Q

Heating plastic in a microwave oven results in plastic having a lower temperature rise than water. Suggest why.

A
  • only water particles absorb microwaves, thus only water is heated
  • the microwaves penetrate the beaker and are thus not absorbed by the plastic
  • the tiny temp rise in plastic is only due to the hot water heating the beaker indirectly through the transfer of thermal energy to its surroundings
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2
Q

What are microwaves absorbed by?

A
  • some are absorbed by water molecules, fats and sugars = to heat food (turns to kinetic energy passed on)
  • some aren’t and thus are used for satellites (and can thus pass through our atmosphere)
  • not absorbed by plastic, glass or ceramics
  • reflected by metal
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3
Q

What happens to light when it hits our eyes?

A
  • light is reflected off objects

- absorbed by the retina

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4
Q

Difference between specular and scattered/ diffused reflection:

A
  • specular - the angle of I = angle of R = on smooth surface - mirror
  • diffused/scattered - the angle of I is not = to angle of R (doesn’t follow the law of reflection) = rough surface - as the incoming ray leaves at diff angle to the one it approaches the surface
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5
Q

Why do alpha particles have a short range?

A

Alpha particles transfer more energy to the material they travel through than gamma rays as they have a higher ionising power. This means that they used their energy to ionise the materials they have come in contact with, meaning they have a shorter range

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6
Q

How do fluorescent light bulbs work?

A

electrons are accelerated through the mercury vapour which ionises some of the mercury atoms, producing more free electrons

  • when this flow of free e- collides with the e- in other mercury atoms, the e- in the mercury atoms are excited to higher energy levels
  • when the excited e- return to their original energy levels, they emit radiation in the UV range of the EM spectrum
  • compound called phosphor coats the inside of the tube and absorbs this radiation, exciting it’s electrons to higher energy levels and these e- cascade down the energy levels, emitting many diff frequencies of radiation, all in the visible part of the EM spectrum
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7
Q

Why can atoms only absorb certain frequencies?

A
  • electrons can only occupy certain energy levels around the nucleus of an atom (1)
  • energy required to jump from one energy level to another corresponds to the energy of the photon
    absorbed (1)
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8
Q

What is a chain reaction?

A
  • In a chain reaction neutrons from one fission reaction trigger other fission reactions.
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9
Q

What is the difference between contamination and irradiation?

A

Contamination: when you take radioactive material inside your body or it is on your skin
Irradiation: there is radioactive material outside your body, but the radiation can travel into your body

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10
Q

Why can’t we carry out fusion on Earth?

A
  • Very high temperatures are required, so the nuclei are moving at very high speeds
  • very high pressures are required, so the nuclei are close enough to fuse
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11
Q

How can you increase the signals received by a microwave dish?

A
  • making dish larger = to reduce diffraction / so wave
    spreads less / to maximise signal received / to
    produce a parallel beam
  • position dish high up / sensible place = (explanation) avoids obstacles / maximise signal
    received / avoids signal loss
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12
Q

Why may features of radioactive isotope not be visible?

A
  • Activity is a random/unpredictable occurrence so may not be constant in a graph
  • Low numbers of counts amplify relative variations
  • (All radioactive isotopes) have a half-life
  • but changes in activity will be small if the half-life is long
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13
Q

When are radioactive levels ok?

A
  • measure levels

- if equal to background radiation then ok

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14
Q

Why might scientists not believe evidence?

A
  • no data / no evidence
  • secrecy
  • cannot be proved/be reproduced / cannot get
    similar or reliable results
  • disagrees with fundamental physics (e.g if fusion can’t occur at low temp and pressure)
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15
Q

What are the problems of dealing with radioactive waste?

A
  • (as gamma is highly penetrating) it must be placed in a material resistant or thick enough (to stop the radiation penetrating)
  • long term containment needed
  • it must be stored where there is no possibility of it
    contaminating water supply
  • they need to monitor levels of radioactivity for long periods of time (as acceptable radioactivity levels may change over time)
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16
Q

Why can starts undergo fusion?

A
  • needs high Pa = nuclei are close together
  • need high temp = more ke so nuclei move faster with high velocity
  • need large gravitational force = pulls it together
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17
Q

What is released in fusion vs fission?

A
  • fusion = a large stable nucleus, energy due to the mass defect (more than fission) and 3 neutrons
  • fission = 2 daughter nuclei, energy due to the mass defect and 3 neutrons
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18
Q

Does the Sun emit radiation equally at all frequencies?

A
  • no
  • 99% of the radiation emitted in the form of visible light, ultraviolet rays, and infrared rays (also known as heat). - high-frequency radiation
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19
Q

How does the Earth’s atmosphere help to protect against UV?

A
  • ozone in the atmosphere absorbs UV
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20
Q

Why do people sunbathe even after knowing the issues?

A
  • to get a tan- vitamin D production
  • improves health - can lower blood pressure
  • the benefit outweighs the risk
  • use protective measure, e.g. high factor sun cream/only do it for short times to keep risk small/ skin cancers can be easily seen and dealt with
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21
Q

Why is alpha not detected?

A
  • all windows block alpha
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22
Q

How does nuclear fission occur in a reactor?

A
  • chain reaction produces energy in the fuel rod
  • fuel rod contains the nuclear fuel for fission
  • control rod absorbs neutrons
  • coolant absorbs heat from the reaction/ transfers heat
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23
Q

Why can calmer waves destroy things inland?

A
  • amplitude is bigger on the shore/ smaller in mid-ocean
  • Wavelength gets smaller as waves slow down as they approach land
  • Large amplitude means more (potential) energy (to cause damage
  • Waves go further inland/can get over barriers
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24
Q

What is background radiation?

A

radiation present in the environment/around us /

radiation that is always present

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25
Q

How does short length radiation damage living cells?

A

they are ionising radiations/can cause ionisation
(ionisation) removes electrons (from atoms/molecules) (
(ionisation) results in chemical reactions /damage DNA/
cause mutations (1)

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26
Q

Why is irradiation less hazardous than contamination?

A
  • no physical contact with source/contamination means physical contact with source
  • so exposed for less time with irradiation
  • irradiation can be screened off/can move away from source
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27
Q

What is background radiation?

A

radiation) all around us /(subjected to) it all the time /

from the environment

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28
Q

Why can smoke detectors be dangerous even after 10 years?

A

(Alpha particles are highly) ionising 
This can damage cells/DNA/cause cancer 
(After 10 years the) activity will still be very high (due to long half-life) 
Am-241 may escape from a discarded detector 
Can be ingested by animals/absorbed by plants / enter the food webs 

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29
Q

What happens when the frequency of waves increases?

A

Speed is unchanged / stays the same 

Wavelength reduces

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30
Q

What is the typical weight of an empty single decker bus?

A

120 000N or 12,000 kg

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31
Q

Why should doctors check the activity of a substance before using it on a patient?

A

To check the activity / intensity / strength of the isotope (1)
Idea that the activity will be continually falling so needs to be monitored (1~)

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32
Q

Using the equation P=IsquaredR explain why the increase in voltage is important to power loss?

A

Very large decrease in power loss (1)

Power loss is related to the square of the current / AW (1

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33
Q

Why may there be anomalies in radioactivity counting?

A

Radiation / activity is random (1)

Randomness is amplified at low readings / AW (1)

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34
Q

Why is a gamma knife safe?

A

Few days between treatments allows healthy cells to be repaired or replaced (1)
Size of dose related to the mass of the patient / age of patient / size of tumour / nature of tumour (1)
Rotation of source reduces damage to healthy cells (1)
BUT rotation of source reduces damage to healthy as time of exposure is shorter (1)
Patient remaining still will reduce the damage to healthy cells (1)

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35
Q

Describe convex lens

A

refraction occurs at boundary between two different mediums
speed of light in air is faster than in glass
refractive index of glass is higher than air
light bends towards normal when entering lens / ORA
lens causes light rays to converge
light rays parallel to the principal axis meet at the focal point
image is inverted / image is after F

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36
Q

How can you design an experiment to check the focal length of a lens?

A
  • focal length is distance between lens and image (of a distant object) or distance between lens and focal point
  • measures thickness of all lenses (with the mm ruler)
  • produce an image (of the tree on the card)
  • measure image distance from tree = which is the focal length - with a metre ruler
  • try all lenses
  • repeat three times
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37
Q

Why would IR not be detected if someone was wearing silver clothing?

A
  • foil reflects IR (back to body

- not enough IR (from body) detected

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38
Q

How would milk heat in an IR oven in a black vs a white bowl?

A
  • black is faster as black absorbs more IR / heat ( than white)
  • white is slower as white reflects more IR /heat (away than black)
39
Q

What properties are common for all EM waves?

A
  • travel at the same speed (through a vacuum)
  • can travel through a vacuum/space
  • transfer energy through transverse waves
  • can be reflected
  • can be refracted
  • can be diffracted
  • can be absorbed
  • can be transmitted
40
Q

Why does refraction happen at the boundary between deep and shallow water?

A
  • velocity is slower in shallow water
  • edge of waterfront entering shallow water slows down
  • but edge of wave in deep water continues at high speed
  • thus change in direction of wavefront
41
Q

Why does no refraction happen at parallel?

A
  • every point hits the boundary at the same timed so it slows down at the same time
42
Q

Why is the contamination of alpha radiation inside the body dangerous?

A
  • alpha radiation is highly ionising
  • an cause an increased risk of cancer, organ failure, radiation sickness, mutations of genes, damage to cells/tissues / organs
  • until the radioactive material is removed, absorbed by body or activity of radioactive material reaches background radiation levels
43
Q

What are the environmental problems of the nuclear power station?

A
  • waste is radioactive
  • waste has a long half-life
  • waste needs to be buried
  • risk of catastrophic accidents - e.g. Fukushima, Chernobyl, Three Mile Island
  • fuel is non-renewable
44
Q

Describe the process of nuclear fission?

A
  • hit by a neutron
  • neutron absorbed by U (nucleus)
  • forms a larger unstable nucleus
  • splits into two (smaller) nuclei/
  • releasing three neutrons and energy
45
Q

Why is something a chain reaction?

A
  • further neutrons released;
  • neutrons released when one atom splits
  • cause further fission;
46
Q

Describe the process of nuclear fusion

A
  • two nuclei(of light elements or smaller atoms) join

- forming a larger / heavier nucleus / one

47
Q

Why are nuclear fusion reactors are not used to produce energy in a power station?

A
  • (currently) only experimental
  • reaction does not last long enough
  • use more energy than they produce
  • difficult to control
48
Q

Where does the energy in fusion come from?

A
  • the mass of the large nucleus (atom) is less than the mass of the smaller nuclei (atoms
  • mass loss converted into energy as e=mcsquared
49
Q

Why is ultrasound used before an operation?

A
  • doctor knows where and what the problem is
  • so the doctor knows how severe/bad the problem is
  • so the doctor knows if a (surgical)operation is needed
50
Q

How does a prism refract light?

A
  • light enters the prism, slows down and refracts towards the normal
  • blue/violet light has more Hz than red so refracts more - bends more towards normal or slows down more
  • due to lack of symmetry refraction when light leaves the prism is not reversed
  • light leaves prism speeds up and refracts again away from normal
  • blue light refracts more due to higher Hz
  • blue and red light travel separately as white light is dispersed into diff Hz/ Wavelengths
51
Q

Why is ultrasound better than surgery?

A
  • less chance of infection
  • does not damage the patient
  • so the patient does not need an operation(to see if anything is wrong)
  • idea of non-ionising
52
Q

What is the difference between contamination and irradiation?

A
  • Contamination occurs when radioactive source/material is on or in the body /object
  • Irradiation occurs when the object is exposed to radiation (from outside of the body /object)
53
Q

How can we protect against radioactive substances?

A 
Keeping a safe distance (from source)
Use tongs 
Point sources away from people
Keep sources in sealed containers 
Keep exposure time as short as possible
Behind lead screen 
Use protective equipment and badge
54
Q

Why is uranium considered to be renewable and non renewable?

A
  • supplies of uranium are large enough / will not run out to consider it renewable
  • but Uranium is not being replaced/used quicker than it is being replaced to consider it non-renewable
55
Q

How is cancer caused by radiation?

A
  • absorb radiation and interact with molecules
  • cause ionisation and produce ions
  • low dose = damage cells and mutations - divide uncontrollably and cancer
  • high doses = kill cells completely = radiation sickness
56
Q

What is the difference between irradiation and contamination?

A
  • irradiation - exposed to radiation but not radioactive - dangerous if beta and gamma irradiated as they can penetrate tissue (alpha stopped by air)
  • contamination - radioactive atoms get in substance as they touched it - beta and gamma will pass out mostly but bone will absorb beta but alpha most dangerous
57
Q

Why do lorries need larger brake pads?

A
  • Lorry has more KE than a car at the same velocity
  • More absorption of energy by larger brake discs
  • Higher rate of dissipation of energy to surrounding air
  • Brakes less likely to overheat
58
Q

How can you reduce friction on a car?

A
  • make it more streamlines

- lubricate tyres or track

59
Q

What do the colours on a thermogram show?

A
  • white / yellow / red / light(er) show most heat loss / highest temperature AW
  • black / dark blue / purple / dark(er) show least heat loss / lowest temperature
60
Q

Why is a cavity wall, with a layer of foam and shiny foil in between good at reducing energy losses?

A
  • traps air in between - air is a good insulator = reduces convection
  • foam is an insulator and thus prevents heat loss
  • shiny foil reflects IR radiation back into the house
61
Q

How were observations about the Universe made and what were the new scientific ideas that followed?

A

Observations:
- early telescopes were not accurate/powerful enough

Distance measurement :

  • distances to remote galaxies are very great
  • distance is measured by brightness
  • distance is measured by parallax
  • CMBR left over from Big Bang

Velocity measurement:

  • redshift
  • greater redshift means greater velocity - accept Hubble’s Law

New ideas:
- measurements show that galaxies are receding / the
Universe is expanding
- (in general) more distant galaxies move faster - this implies that all started at one point
- the β€œBig Bang” occurred about 14 000 million years ago
- The Milky Way is not the only galaxy / there are many
others outside the Milky Way

62
Q

What is the difference between a comet and an asteroid?

A

Comet:
- have a tail, contain ice and dust and rock

Asteroid:
- no tail and found in asteroid belts and rocky

63
Q

What is the relationship between distance to galaxies and their speeds?

A
  • further away the faster the galaxy’s motion
  • space is expanding
  • big bang / all galaxies started in the same place
64
Q

How do scientists know there is hydrogen in the stars?

A

spectral lines
idea of being unique to an element / matching the
hydrogen spectrum

65
Q

How does a star’s mass affect the life of a star?

A
  • Physical differences: e.g. High mass stars have:
    higher core temp – higher pressures – higher density -
    higher luminosity - heavier/more massive nuclei formed
  • Low mass: protostar, main sequence, red giant, planetary nebula, white dwarf
    dwarf (accept planetary halo, brown dwarf)
  • High Mass: protostar, main sequence/supergiant, red
    (supergiant) giant, supernova, neutron star or black
    hole
66
Q

How are neutron stars formed?

A

(from a) super giant / very massive star
idea of remnant/core/left over
not massive enough to form a black hole

67
Q

How is energy transferred from the core of the star to the surface?

A

photons / radiation

convection (currents)

68
Q

Why do bigger stars stay in the main sequence phase for a shorter period of time compared to smaller stars?

A

Much higher temperature/pressure
Fusion happens more quickly
Hydrogen used up more quickly
Even though more hydrogen in star

69
Q

How is the solar system formed?

A

dust and gas 

pulled together by gravity

70
Q

Why may a single wind turbine be an unreliable source of energy?

A

(Idea of) not always enough wind/demand may exceed supply

71
Q

What is redshift?

A

When a light source is moving away the light that it emits is stretched so that it is shifted towards the red (longer wavelength) end of the spectrum. The faster it is moving the more the light is red-shifted.

72
Q

What happens to red-shifted light?

A

Light is stretched (1)
wavelength increases and frequency decreases.
(1)

73
Q

What does a blue star tell you about the type of radiation emitted?

A

It means that the surface temperature is high (1)
so it is emitting much more radiation in the blue
part of the spectrum. (1)

74
Q

What is the job of the wires in a circuit?

A
  • live wire = carries the voltage (p.d.) and alternates between a + and - voltage of about 230V
  • earth wire = is for safety and carries the current away of something goes wrong and at voltage of 0V
  • neutral wire = completes the circuit = when appliance is operating normally, current flows through the live and neutral wire and around 0V
75
Q

Why are crumple zones used?

A
  • more collision time and distance
  • thus less acceleration
  • force = change in momentum/ time so a longer collision time = means a smaller rate of change of momentum
76
Q

What are the typical speeds for walking, running, cycling, cars, breeze, gale, sound and train?

A
  • walking = 1.5 m/s
  • running = 5 m/s
  • cycling = 7 m/s
  • cars = 22 m/s (13 m/s if built up areas and 31m/s in motorway)
  • breeze = 5 m/s
  • gale = 20 m/s
  • sound = 340 m/s
  • train = 55 m/s
77
Q

What calculations are needed to measure human reaction time?

A
  • use v^2 - u^2 = 2as
  • v = 0, a = 10m/s and s = distance in m
  • then use s=d/t
  • use u as s and d as distance in m
78
Q

Can you figure out thinking distance?

A
  • speed*reaction time (0.2 sec)
79
Q

How do brakes stop a car?

A
  • brakes do work on the car’s wheels
  • transfers energy from cars ke store to thermal store of brakes
  • to stop car - brakes must transfer all of this energy
  • double mass = double braking distance
80
Q

What is a collision?

A
  • large negative acceleration/ declereation
81
Q

What is the mass of a car, a single-decker bus and a loaded lorry?

A
  • car = 1000 kg
  • single decker bus = 10,000 kg
  • loaded lorry - 30,000 kg
82
Q

How do seatbelts allow you to come to a slower stop?

A
  • the car stops = person continues to move forwards
  • seatbelt stretched to stop
  • if no seatbelt = acc at original speed = large force
  • need to be replaced after a crash
83
Q

How do safety items such as crumple zones reduce force?

A
  • force lowered by slowing the object down over a longer time = more collision time and distance
  • decreasing deceleration as a=change in speed/time
  • longer it takes for change in momentum = smaller force acting
84
Q

How can you calculate deceleration knowing the force, speed, reaction time, distance and mass?

A
  • f=ma

- so a = f/m

85
Q

Why should electric cars not be used?

A
  • charging ports are expensive and the cost of batteries is high
86
Q

Why may more fuel than expected be used in a car?

A
  • traffic is heavy / needs to stop and start a lot / lots of braking
  • large load carried / increased number of passengers /towing/heaters/
  • hilly / bends / wet/ windy
  • heavy braking / rapid acceleration / wrong
87
Q

How can ventilation holes reduce braking distances?

A
  • heat dissipated/transferred (to air) more quickly
  • KE is reduced more quickly
  • comes to stop quicker
88
Q

Describe red shift:

A
  • The further away a galaxy is the more red shifted it is indicating an expanding universe
  • If galaxies are moving away then the universe must be expanding
  • If whole universe is expanding then it must have started from a certain point –the singular point where the Big Bang occurred
  • More distant galaxies are more red shifted than stars that are closer
  • Distant galaxies show the lines moving towards the red end of the spectrum
  • Dark bands are moving towards the red end of the spectrum
  • Red shift is caused by a change in frequency / wavelength of light
  • changes in frequency and wavelength of light from distant galaxies
  • Red shift shows galaxies moving away.
89
Q

What is the Big Bang?

A
  • describes the origin of the Universe
  • all matter concentrated at a (single) point
  • single massive explosion (sending matter outwards)
90
Q

What is the universe?

A
  • an innumerable collection of galaxies or a large number of galaxies
91
Q

How is redshift evidence for the big bang theory?

A
  • The spectra of stars contains black lines.
  • These black lines correspond to very specific wavelengths of light absorbed by certain atoms in the star.
  • All stars contain Hydrogen and Helium atoms.
  • Hence all spectra from stars contain a series ofvery specific black lines (distinct pattern of separated lines)
  • These black lines are seen shifted in the spectrafrom distant stars towards longer wavelengths.
  • Implies light from distantstars has undergone a Doppler shift
92
Q

How is CMBR evidence for the big band theory?

A
  • The Big Bang Theory states that all the matter and energy of the universe was concentrated at a single point.
  • At the start of the universe, this energy was high energy gamma radiation.
  • Since the universe has been expanding, these gamma waves have stretched out.
  • They are now seen as longer wavelength microwaves.
  • And are seen uniformly in all directions in the universe- implying they all must have started at the same point
93
Q

What is the typical acceleration of a bike and a car?

A
  • bike = 1 to 2.5 m/s

- car = 3 to 4 m/s

94
Q

What is thermal conductivity?

A
  • tells you how quickly energy is transferred through a wall that’s 1m thick, 1m squared area and temp diff of 1 degrees
  • more = quicker heat loss

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