Physics Flashcards
(363 cards)
1
Q
How many energy stores are there?
A
8
2
Q
Name all 8 energy stores
A
Kinetic, thermal, gravitational potential energy, elastic potential energy, electrostatic, magnetic, chemical and nuclear
3
Q
What is the kinetic energy equation?
A
Kinetic Energy = 1/2 x Mass x Velocity^2
4
Q
How is KE transferred to an object?
A
When the object speeds up
5
Q
How is KE transferred from an object?
A
When the object slows down
6
Q
What are two factors that affects the KE of an object?
A
It’s mass and it’s velocity
7
Q
What would happen to the KE of an object if you were to double it’s speed?
A
The speed would increase by a factor of 4
8
Q
What is the gravitational potential equation?
A
Gravitational Potential = Mass x Gravity x Height
9
Q
Define conservation of energy
A
Energy an be stored, transferred between stores and dissipated - but it can never be created or destroyed. Therefore, the total energy of a closed system has no net change
10
Q
What are the four ways energy can be transferred?
A
Radiation, heating, electrically and mechanically
11
Q
Define energy transfer by radiation?
A
Energy transferred by waves
12
Q
Define energy transfer by heating?
A
Energy transferred from a hotter object to a colder object
13
Q
Define energy transfer by electrically?
A
A charge doing work
14
Q
Define energy transfer by mechanically?
A
A force acting on an object
15
Q
Give an example of energy transfer by radiation
A
Energy from the Sun reaching Earth by light
16
Q
Give an example of energy transfer by heating
A
Heating a pan on a hob
17
Q
Give an example of energy transfer electrically
A
Charges moving around a circuit
18
Q
Give an example of energy transfer mechanically
A
Pushing, stretching or squashing an object
19
Q
Define useful energy
A
Energy transferred from a store to a useful store
20
Q
What is the efficiency equation?
A
Efficiency = Useful Energy / Total Energy
21
Q
What are methods of reducing wasted energy?
A
Lubrication or thermal insulation
22
Q
How does lubrication reduce wasted energy?
A
By reducing friction
23
Q
What type of energy transfer is friction?
A
Mechanical (Kinetic -> Thermal)
24
Q
How does insulation reduce wasted energy?
A
By reducing release of thermal energy
25
Describe the process of conduction
Particles are heated, making them hotter
Particles vibrate more and collide with each other
This transfers energy from their KE stores to other particles which then vibrate faster
26
What does conduction do?
Transfers energy through objects
27
What does thermal conductivity describe?
How well a material transfers energy by conduction
28
Give an example of a type of material with a high thermal conductivity
Metals (Copper)
29
Give an example of a material with a low thermal conductivity
Gases (Air)
30
What are ways a house is designed to reduce thermal conductivity?
Double-glazing windows
Cavity walls
Thick walls
31
How does the thickness of a wall affect the rate of energy transfer?
The thicker the wall, the slower the rate of energy transfer
32
What is an example of a non-renewable fuel?
Fossil fuels and nuclear fuels
33
Describe the cost of afossil fuel plant?
Relatively cheap
34
Describe the cost of a nuclear power plant?
Very costly
35
What are the disadvantages of non-renewable usage?
Contribution to greenhouse effect
Oil spillages
Risk of nuclear explosion
36
List examples of renewable energy sources?
```
Bio-fuels
Wind Power
Solar Power
Hydro-electric Power
Tidal Power
```
37
What is an advantage of using renewable energy sources?
Don't damage the environment as much as non-renewable sources
38
What is a disdvantage of using renewable energy sources?
Don't release as much energy and not reliable as some depend on the weather
39
What are biofuels?
Renewable energy resources created from either plant products or animal dung
40
Why is it arguably carbon neutral?
If you plant trees at the rate you're burning them
41
What are the advantages of biofuel?
Reliable
| Short time to grow
42
What are the disadvantages of biofuel?
Can't respond to immediate energy demands
Very high to refine the fuels
Wasting resources for plants grown for food (water and space)
43
What are the advantages of wind power?
Low running costs
| No pollution
44
What are the disadvantages of wind power?
```
Expensive to setup
Unsightly and noisy
Less efficient than non-renewable
Can't respond to high demand
Unreliable
```
45
What are solar cells made from?
Materials that use energy transferred by light to create and electric current
46
What are the advantages of solar power?
No running costs
| No pollution
47
What are the disadvantages of solar power?
Expensive to setup
Doesn't work at night
Can't respond to high demand
48
What does HEP usually involve?
Flooding a valley
49
What are the advantages of HEP?
Immediately respond to increased electricity demand
Low running costs
Reliable
No pollution
50
What are the disadvantages of HEP?
Loss of habitats
Risk of flooding
Expensive to setup
51
How does tidal power work?
Tide come's in to fill up the estuary
| Water is then let out through turbines which generates electricity
52
What are the advantages of tidal power?
No pollution
Reliable
No fuel costs
Low running costs
53
What are the disadvantages of tidal power?
Affects boat access
Spoils the view
Loss of habitats
Moderately high setup cost
54
What is most of the UK's energy produced from?
Non-renewable
55
Why are smaller energy providers reluctant to change energy source?
It costs money to invest in renewable energy
56
Why is research into improving the reliability and cost of renewable resources bad?
Costs time and money
57
Why are personal changes hard to achieve?
Expensive
58
What do waves transfer?
Energy and infomation
59
What is the amplitude of a wave?
The displacement from the rest position to a crest
60
What is the wavelength of a wave?
The length of a full cycle of the wave
61
What is the frequency of a wave?
The number of complete cycles of the wave passing a certain point per second
62
What is frequency measure in?
Hertz
63
What does hertz actually equal?
One wave per second
64
What is the period of a wave?
The number of seconds it takes for one full cycle
65
How do you calculate the period of a wave?
Period = 1 / Frequency
66
Describe the direction of a transverse wave
Perpendicular to the direction the wave travels
67
Describe the direction of a longitudinal wave
Parallel to the direction the wave travels
68
Give some examples of transverse waves
Electromagnetic waves
S-waves
Ripples and waves in water
69
Give some examples of longitudinal waves
Sound waves
| P-waves
70
How do longitudinal waves actually move?
By making compressions (high pressure) and rarefactions (low pressure)
71
In terms of longitudinal waves, describe compressions
High pressure and lots of particles
72
In terms of longitudinal waves, describe rarefactions
Low pressure and few particles
73
What is the wave speed equation?
Wave Speed = Distance / Time
Or
Wave Speed = Wavelength x Frequency
74
What can you use to measure the speed of sound?
An oscilloscope
75
Describe how to use an oscilloscope to measure the speed of sound
Line up the microphones so waves align but have moved exactly one wavelength apart
Measure the distance between the microphones to find one wavelength
76
What can you use to measure the speed of water ripples?
A strobe light
77
Describe how to use a strobe light to measure the speed of water ripples
Use signal generator to set water waves to a certain frequency
Alter the frequency of the strobe light until the wave pattern on the screen appears to freeze
Then measure the distance between lines that are 10 wavelengths apart then find the average wavelength
78
What can you use to measure the speed of waves in solids?
Peak Frequency
79
Describe how to use peak frequency to find the speed of waves in solids
Measure and record the length of a metal rod
Tap the rod with a hammer and write down the peak frequency displayed by the computer
Repeat this three times to get an average peak frequency
Calculate the speed using V = fλ (λ = twice the length of the rod)
80
What three things can occur when a wave hits a boundary?
Absorbed, transmitted or reflected
81
What happens to wave when it's absorbed?
The wave transfers energy to the material's stores
82
What happens to wave when it's transmitted?
The wave carries on travelling through the new material
83
What happens to wave when it's reflected?
The wave is sent back away from the second material
84
How does different density materials affect wave speed?
The denser the material, the slower the wave
85
What happens to a wave when it hits a boundary at an angle?
Speed and direction changes
86
What happens to a wave when it hits a boundary along the normal?
Speed change but no change in direction
87
How does change in speed affect how much a wave bends?
The greater the change in speed, the more a wave bends
88
When will a wave refract towards the normal?
If it slows down
89
When will a wave refract away from the normal?
If it speeds up
90
What affects how much a wave will refract?
It's wavelength, shorter wavelengths bend more
91
What doesn't change during refraction?
A wave's frequency
92
What does change during refraction?
A wave's speed and wavelength
93
What is the normal?
A line that is at 90* to the boundary
94
What causes sound waves?
Vibrating objects
95
What determines what an object can transmit?
It's size, shape and structure
96
How are the vibrations in a sound wave passed through?
By a series of compressions and rarefactions
97
True or False? Sound travels at different speeds in different media?
True
98
Compare the speed of sound waves in all three of the states of matter?
Solid > Liquid > Gas
99
Why can't sound waves travel in space?
Because there are no particles to move or vibrate
100
Describe how the ear detects sound?
Sound enters eardrum causing it to vibrate
Vibrations passed along to ossicles through the semicircular canals and to the cochlea
Cochlea turns these signals into electrical signals which get sent to your brain
101
How does frequency affect pitch?
A higher frequency means a higher pitch
102
What limits the human hearing?
Size and shape of the eardrum
103
What is ultrasound?
A sound with frequencies higher than 20,000Hz
104
True or False? Ultrasound is the lowest possible frequency a human can hear?
False
105
What happens when an ultrasound hits a boundary?
It gets partially reflected
106
What is partial reflection?
When a wave passes from one medium to another, some of the wave is reflected off the boundary and some is transmitted
107
What are uses of ultrasound?
Medical imaging and industrial imaging
108
How is ultrasound used in medical imaging?
Ultrasound waves can pass through the body but whenever they reach a boundary some of the wave is reflected back and detected
The exact time and distribution of these echoes are processed by a computer to produce a videoo image of the foetus
109
How safe is ultrasound?
As far as we know, it's completely safe
110
How is ultrasound used in industrial imaging?
Ultrasound can also be used to find flaws in objects
Ultrasound waves entering a material will usually be reflected
If there is a flaw, the waves will be reflected soon
111
In sonar, how do you calculate the distance the wave has travelled?
Distance = Speed x Time
112
In sonar, how do you calculate the depth of the sea?
Distance = (Speed x Time) / 2
113
What is infrasound?
A sound with frequencies lower than 20
114
Name some examples of animals that communicate using infrasound
Elephants and whales
115
Name some uses of infrasound
Animal communication and natural disaster detection
116
What causes seismic waves?
Earthquakes and explosions
117
Name two seismic waves
P-waves and S-waves
118
What can scientists understand through seismic waves?
The structure of the Earth
119
What type of wave is a P-wave?
Longitudinal
120
What state can P-wave's travel through?
Solids and liquids
121
Describe the speed of a P-wave?
Faster than S-waves
122
What type of wave is a S-wave?
Transverse
123
What state can S-wave's travel through?
Solid
124
Describe the speed of a S-wave?
Slower than P-waves
125
True or False? The angle of incidence = Angle of reflection - 180?
False, angle of incidence = angle of reflection
126
State the law of reflection
Angle of incidence = Angle of reflection
127
What is the angle of incidence?
The angle between the incoming wave and the normal
128
What is the angle of reflection?
The angle between the reflected wave and the normal
129
What is the normal?
An imaginery line that's perpendicular to the surface at the point of incidence
130
What is total internal reflection?
When a wave is reflected back into the material
131
When can TIR occur?
More dense material towards a less dense
132
When does TIR occur?
When the critical angle is exceeded
133
What is the critical angle?
The angle of incidence beyond which rays of light passing travel perpendicular to the normal (parallel to the normal)
134
What are the two types of reflection?
Specular and diffuse
135
When does specular reflection occur?
When waves are reflected in a single direction by a smooth surface
136
When does diffuse reflection occur?
When waves are reflected by a rough surface and the waves are reflected in all directions
137
Why does diffuse reflection occur?
Because the normal is different for each incident ray so each ray has a different angle of incidence and because of angle of incidence = angle of reflection the angle of reflection is different aswell
138
What do you do with the glass block when investigating refraction?
Trace around it and use a ray box to shine light through it
139
Once the glass block has refracted the light, what do you do?
Trace the incident ray and the emergent ray and then join up the rays with a straight line
140
Once all the rays are drawn, when investigating refraction, what do you do next?
Use a protractor to measure the angles and repeat whole experiment and calculate an average
141
What should you see when investigating refraction?
Ray bends towards normal on entry of the glass and then bends away from the normal on exit of the glass
142
What does the colour and transparency of a colour depend on?
The wave's absorbed wavelength
143
What do opaque objects not do?
Transmit light
144
What do transparent objects do?
Transmit light
145
What do translucent objects do?
Absorb and reflect light
146
How do colour filters work?
They only let through particlular wavelengths of light
147
What are colour filters used to?
Filter out different wavelengths of light, so that only certain colurs are transmitted
148
How do secondary colour filters work?
They allow both primary colours that make that colour through
149
Name the two types of lens
Diverging and converging
150
Describe the shape of a converging lens
Bulges outwards in the middle
151
Describe the shape of a diverging lens
Caves inward
152
What does a converging lens do?
Causes parallel rays of light to be brought together at the principal focus
153
What does a diverging lens do?
Causes parallel rays of light to spread out
154
Where is the principal focus in a converging lens?
Where rays hitting the lens parallel to the axis all meet
155
Where is the principal focus in a diverging lens?
Where rays hitting the lens parallel to the axis appear to all come from
156
What is the focal length?
The distance from the centre of the lens to the principal focus
157
What is a virtual image?
An image that is created when light rays appear to be coming from a completely different place to where they're actually coming from
158
What is a real image?
An image that is created when light rays come together to form an image
159
What image can be captured on a screen?
Real
160
What image can't be captured on a screen?
Virtual
161
What increases the power of a lens?
It's curvature
162
What lens has a postive power?
Converging
163
What lens has a negative power?
Diverging
164
What does a stronger lens mean?
The more strongly it converges rays of light
165
True or False? Some materials are better at focusing light than others?
True
166
On a ray diagram, what does a diverging lens look like?
>-------------
167
On a ray diagram, what does a converging lens look like?
168
On a diverging lens diagram, how do you locate the virtual image?
Mark the point where the virtual ray meets the ray that goes through the middle
169
What type of waves are EM waves?
Transverse
170
True or False? EM waves all travel the same speed everywhere?
False, although they travel at the same speed in a vaccum, they travel at different speeds in different materials
171
How are EM waves generated?
By changes in atoms and it's nuclei
172
How are gamma rays created?
When a positron collides with an electron
173
How are visible light rays created?
Change in electron energy levels
174
What do all EM waves transfer?
Energy from a source to an absorber
175
How do you increase the amount of energy an EM wave transfers?
By increasing the frequency
176
How do radio waves interact with the human body?
Transmits through without being absorbed
177
How do micro waves interact with the human body?
Some transmits, however some is absorbed causing the heating of cells
178
How do visible and infared waves interact with the human body?
Mostly reflected or absorbed by the skin, however, if too much can burn the skin
179
How do ultraviolet waves interact with the human body?
Is absorbed by the skin, however, due to it's higher frequency it is dangerous (carcinogenic)
180
How do x-ray and gamma waves interact with the human body?
Either reflected, transmitted or absorbed as it depends on the deepness of the tissue and can cause mutations and damage to cells
181
True or False? Only certain objects emit EM radiation, this is because not all atoms are unstable?
False, all objects absorb and emit EM radiation
182
What does the distribution and intensity of the EM emitted depend on?
The objects temperature
183
How does temperature change the EM wave emitted?
The hotter the object, the more intense the emitted wavelength
184
What happens to the radiation emitted to the Earth from the Sun?
Some of it is reflected but most of it is absorbed
185
Why does it get colder at night?
Because Earth emits it's radiation which causes a decrease in temperature
186
How do you investigate what surfaces/colour are better emitters?
Wrap test tubes in the same material but with a different colour or surface
Add boiling water to the test tubes (same volume)
Measure temp (thermometer)
Temperature that drops the most will be best emitter
187
What are EM waves made up of?
Oscillating electric and magnetic fields
188
Name one thing made up of oscillating electric charges?
Alternating currents
189
How can you produce EM waves with an AC?
Make transmitter oscillate to create the radio waves
Reciever absorbs radio waves, energy carried by the waves are transferred to the electrons in the circuit
The current will have the same frequency as the radio wave that generated it (and vice versa)
190
What is the main use for radio waves?
Communication and broadcasting
191
Compare long-wave to short-wave radio
Long-wave radio can be recieved halfway around the world this is because they can bend around the curved surface of Earth
Short-wave radio can be recieved from long distances aswell, however, this is because they are reflected by the Earth's atmosphere
192
How does bluetooth work?
By sending short-wave radio waves
193
What type of waves do TV and FM radio use?
Very short radio waves
194
What do satellites use to communicate?
EM waves
195
How does a satellite work to transmit TV?
TV sends it's signal into space where the satellite picks it up and reflects it back to Earth where a satellite dish recieves it
196
How do microwave ovens work?
By transmitting microwaves that are absorbed by the water molecules in food which then heats the food
197
How are the microwaves in a microwave different to satellites?
Microwaves in satellites need to pass through the Earth's watery atmosphere whilst microwaves in microwaves need to transmit through the food a bit and then be absorbed
198
What are some uses of IR radiation?
To monitor temperature, security systems and transmit infomation
199
How does IR radiation monitor temperature?
It detects the radiation and transmits it into an electrical signal
200
How can IR radiation be used to heat foods?
Object emits IR which then transfers into the thermal energy in the object that is being heated
201
Give some uses of IR radiation when transfering infomation
Optical fibers and TV remotes
202
What do optical fibers use?
Total Internal Reflection
203
Give uses of visible light
Photography and vision
204
Give uses of ultraviolet waves
Fluorescent lights, security pens and the sterilising of water
205
Give uses of x-rays
Medical imaging and airport security
206
Why can x-rays be used to "see-through" objects?
Because x-rays are transmitted by flesh but absorbed by denser material (bones or metal)
207
Give uses of gamma rays
Sterilising, medical imaging and cancer treatment
208
Why are gamma rays used to sterilise stuff?
Because the gamma rays kill microbes
209
Why are gamma rays used to treat cancer?
The radiation can be targeted to kill cancer cells
210
Define a scalar
A quantity with only magnitude, not direction.
211
Define a vector
A quantity with magnitude and direction
212
What is the difference between a scalar and a vector?
A scalar has only magnitude and no direction whilst a vector has magnitude and direction
213
Give examples of a scalar quantity
Speed and distance
214
Give examples of a vector quantity
Velocity and displacement
215
What is the acceleration equation?
Acceleration = Change in velocity / Time
216
What is the uniform acceleration equation?
Final velocity - Inital velocity = 2 x Acceleration x Distance
217
What does the gradient equal in a distance time graph?
The speed of the object
218
What does a flat section equal in a distance time graph?
Where the object has stopped
219
What does a curve equal in a distance time graph?
Where the object is accelerating
220
What does the gradient equal in a speed time graph?
The acceleration of the object
221
What does a flat section equal in a speed time graph?
Steady speed
222
What does a uphill equal in a speed time graph?
Acceleration
223
What does a downhill equal in a speed time graph?
Deceleration
224
What does the area under the graph equal in a speed time graph?
The distance covered
225
What is newtons first law?
If the resultant force on a stationary object is zero, the object will remain stationary. If the resultant force on a moving object is zero, it'll just carry on moving at the same velocity
226
What is newtons second law?
The larger the resultant force acting on an object, the more the object accelerated (Force = Mass x Acceleration)
227
What is newtons third law?
Whenever two objects interact, they exert equal and opposite forces on each other (every action has an equal and opposite reaction)
228
Why are large decelerations of objects dangerous?
High force required (F=ma)
229
How can you reduce the risk during large decelerations?
By increasing time (decreasing deceleration)
230
Give examples of how a car reduces large decelerations?
Seat belts stretch, crumple zones and air bags
231
Define mass
The amount of matter in an object
232
What type of quantity is mass?
Scalar
233
Define weight
The force acting on an object due to gravity
234
What type of quantity is weight?
Vector
235
What are the units for mass?
Grams
236
What are the units for weight?
Newtons
237
What is the equation for weight?
Weight = Mass x Graviational Field Strength
238
How does distance from an object affect graviational field strength?
The closer you are to the mass, the stronger the graviational field strength
239
When an object is travelling in a circular motion, what remains the same?
The objects speed
240
When an object is travelling in a circular motion, what changes constantly?
The objects velocity (direction)
241
When an object is travelling in a circular motion, where does the force act towards?
The centre of the circle
242
When investigating the motion of a trolley on a ramp, what do you measure the mass of?
The trolley, the unit masses and the hook
243
When investigating the motion of a trolley on a ramp, what do you measure the length of?
The piece of card which interupts the light gate beams
244
What is inertia?
The tendency for motion to remain unchanged
245
What does an object's inertial mass measure?
How difficult it is to change the velocity of an object
246
Why do objects move although 'equal and opposite reactions'?
Depends on the mass as (Force / Mass = Acceleration)
| So less mass will have a greater acceleration
247
What is momentum
The amount of oomph an object has
248
Define momentum
The product of the object's mass and velocity
249
What is the equation for momentum?
Momentum = Mass x Velocity
250
How does the mass of an object affect its momentum?
The higher the mass, the larger the momentum
251
How does the velocity of an object affect its momentum?
The higher the velocity, the larger the momentum
252
What type of quantity is momentum?
Vector
253
What is conservation of momentum?
In a closed system, the total momentum before an event is the same as after the event
254
If an object has zero velocity, what is it's momentum?
Zero (Anything times 0 is 0)
255
What causes changes in momentum?
Forces
256
What is the equation for change in momentum?
```
Force = Change in momentum / Time
Force = Mass x (Final Velocity - Inital Velocity) / Time
```
257
What is the equation for stopping distance?
Stopping Distance = Thinking Distance + Braking Distance
258
What is the thinking distance?
The distance the car travels in the driver's reaction time
259
What is the drivers reaction time?
The time between noticing the hazard and applying the breaks
260
What affects the thinking distance?
Speed and reaction time (tiredness, drugs and alcohol)
261
What is the braking distance?
The distance taken to stop once the brakes have been applied
262
What affects the braking distance?
Speed, mass, condition of brakes and the friction between the car and the road
263
When measuring reaction times with a ruler, how do you compare results?
The longer the distance, the longer the reaction time
264
When measuring reaction times with a ruler, why should you do lots of repeats?
Test is extremely inaccurate
265
What is the reaction time of a typical driver?
One second
266
To avoid an accident, what must drivers do?
Leave enough space in front so they could stop safely (at least more than the stopping distance)
267
Why are speed limits important?
Because speed affects stopping distances alot
268
How does speed affect thinking distance?
As speed increases, thinking distance increases at roughly the same rate (reaction time stays roughly the same)
269
How does speed affect braking distance?
If speed is times by 2, braking distance will be times by 4 (2²)
270
What is the equation for work done by the brakes?
Braking force x Braking distance = 1/2x(Mass x Velocity²)
271
What do electrons sit in?
Different energy levels (shells)
272
How can a inner electron move to a higher energy level?
By absorbing electromagnetic radiation with the right amount of energy
273
What has happened when an electron is 'excited'?
It has moved up to an empty or partially filled shell
274
What will happen after an electron becomes 'excited'?
The electron will quickly fall back to its original energy level and in doing so will emit the same amount of energy absorbeb
275
How is the energy carried away when an electron moves back to it's original energy level?
By an electromagnetic wave
276
What does the part of the electromagnetic wave emitted depend on?
The energy
277
As you get further from the nucleus what happens to the levels?
They get closer together
278
What happens when an atom is ionised?
It loses an electron (Atom is now positively charged)
279
What ionises atoms?
Ionising radiation
280
What is ionising radiation?
Any radiation that can knock electrons from atoms
281
What are isotopes?
Different forms of the same element
282
What do unstable isotops do?
Radioactive decay
283
Why do unstable isotops radioactively decay?
Because they attempt to become stable
284
What do radioactive substances spit out?
Alpha, beta and gamma radiation but also neutrons
285
What are alpha particles?
Helium Nuclei (2 protons + 2 neutrons)
286
How penetrative is alpha radiation?
Not very
287
What stops alpha radiation?
5 cm of air or a thin sheet of paper
288
Why is alpha radiation extremely ionising?
Because of its size
289
What are beta particles?
Either a fast-moving electron or a fast-moving positron
290
How penetrative is beta radiation?
Moderately
291
What stops beta radiation?
Meters of air or a sheet of aluminium
292
Which type of beta radiation has a shorter range?
Positive because it contains positrons and when they hit an electron they destroy each other and produce gamma rays
293
What are gamma rays?
High frequency, low wavelength electromagnetic wavess
294
How penetratative is gamma radiation?
Extremely as they penetrate far into materials without being stopped
295
What stops gamma radiation?
Thick sheets of lead or meters of concrete
296
When is gamma radiation created?
When a nucleus decays and it undergoes nuclear rearrangement and releases energy
297
What are nuclear equations ways of showing?
Radioactive decay
298
How are nuclear equations written?
Atom before decay -> Atom after decay + Radiation emitted
299
What is the one 'golden rule' with nuclear equations?
The total mass and atomic numbers must remain equal on both sides
300
How does alpha decay affect the atom?
Decreases the charge and mass of the nucleus (by 2 and then 4)
301
How does beta-minus decay affect the atom?
Increases the charge of the nucleus
302
How does beta-plus decay affect the atom?
Decreases the charge of the nucleus
303
How does neutron emission affect the atom?
Decreases the mass of the nucleus
304
How are beta-minus particles formed?
A neutron turns into an electron and proton
| Electron then leaves nucleus
305
How are beta-plus particles formed?
A proton turns into an neutron and positron
| Positron then leaves nucleus
306
True or False? Radioactivity is a totally random process?
True
307
What do radioactive sources contain?
Radioactive isotopes that give out radiation from the nuclei of their atoms
308
What is activity?
The rate at which a source decays
309
What are the units for activity?
Becquerels (Bq)
310
What does 1 becquerel equal?
1 decay per second
311
How can you measure activity?
By using a Geiger-Muller tube and counting the amount of clicks
312
What happens each time a radioactive nucleus decays?
One more radioactive nucleus disappears which causes the activity as a whole to decrease
313
What is half-life?
The average time taken for the numer of radioactive nuclei in an isotope to halve
314
What does a short half-life mean?
The activity falls quickly
315
What does a long half-life mean?
The activity falls slowly
316
Where does background radiation come from?
Human activity, space, food, buildings and rocks
317
What is the absorbed radiation dose?
The amount of radiation you're exposed to
318
What are ways of reducing irradiation?
Lead-lined boxes, barriers and remote-controlled arms
319
Why is contamination of unwanted radioactive atoms bad?
If they get stuck, they will decay and release radiation
320
When are contaminated people at risk of harm?
Until the source is removed or all the atoms have decayed
321
How does radiation damage cells?
Radiation will ionse the atoms and molecules within the cells
322
How do lower doses affect cells?
Cause minor damage without killing the cells or mutation of cells
323
How do higher doses affect cells?
Kill cells completely causing radiation sickness (vomitting, tiredness and hair loss)
324
Compare the risk of radiation outside the body
Beta and gamma are the most dangerous with alpha being less dangerous as it can't penetrate the skin
325
Compare the risk of radiation inside the body
Alpha sources are the most dangerous as it's the most ionising
326
What radiation has the biggest risk with contamination?
Alpha
327
What radiation has the biggest risk with irradiation?
Beta or gamma
328
How does activity affect the danger of a radiation?
The higher the activity, the more dangerous the radiation
329
When choosing a radioactive source for an application, what must you look for?
Look to find a balance between a source that has the right level of activity but also the right half life
330
How do fire alarms work?
Uses weak source of alpha radiation and two electrodes
Source causes ionisation and a current flows
If there is a fire the smoke will absorb the particles and prevent the current
331
Why can gamma rays be used to steralise?
A high dose of gamma rays will kill all microbes
332
Why is irradiation better than boiling?
Irradiation doesn't involve high temperature which would ruin fresh ruit or plastic instruments
333
What would the radioactive source be like for sterilisation?
Strong emitter and long half-life
334
What isotopes must be put into a body?
Only gamma and beta (never alpha, unless for cancer treatment)
335
What would the radioactive source be like for tracers?
Short half-life
336
How else is gamma used?
To detect leaks in underground pipes
337
How else is beta radiation used?
Thickness control
338
Why must beta radiation be used when measuring thickness control?
Because gamma will completely transmit through but also alpha won't even make it to the object
339
What is PET scanning a technique for?
To show tissue or organ function and diagnosis of medical conditions
340
What do you inject into the patient?
A substance used by the body with a tracer
341
What occurs once the substance is injected into the patient?
The positrons will be emitted which will them meet electrons and annihilate which will then emit gamma rays
342
How can a tumour be found in a PET scan?
By triangulation
343
What types of radiation are used to treat tumours internally?
Alpha and beta
344
What types of radiation are used to treat tumours externally?
Gamma
345
Describe the half-life of internal treatment of tumours
Short to limit the amount of exposure time
346
Describe the half-life of external treatment of tumours
Long to prevent the need to replace
347
What is nuclear fission?
The splitting up of big atomic nuclei
348
What is nuclear fission used to do?
Release energy from uranium atoms
349
Describe the process of nuclear fission
A slow-moving neutron is fired at a large, unstable nucleus
| The nucleus absorbs the nuetron and causes it to split
350
What is created when U-235 splits?
Two new lighter elements (daughter nuclei and energy)
351
How is nuclear fission a chain reaction?
When the uranium atom splits up, it also spits out two or three neutrons which can hit other uranium nuclei
352
What is the name of the slow-moving neutrons in nuclear fission?
Thermal neutrons
353
How are neutrons slowed down?
By placing the fuel rods in a moderator
354
How do control rods work?
Limit the rate of fission by absorbing excess neutrons
355
What would happen if nuclear fission was left?
Large amounts of energy would be released resulting in a runaway reaction which could cause an explosion
356
What is nuclear fusion?
The joining of small nuclei
357
True or False? The mass of the heavier nucleus equals the mass of the two seperate, light nuclei?
False, because some of the mass is converted to energy
358
What conditions must fusion occur in?
High temperature and pressure
359
What temperature is needed for fusion?
10,000,000*C
360
Why is such a high temperature needed for nuclear fusion?
To overcome the high electrostatic repulsion as the positively charged nuclei have to get very close
361
Why is it really hard to create the right conditions for fusion?
No material can withstand that kind of temperature
362
What are the pros of nuclear power?
```
Pretty safe
Very reliable
Doesn't release bad gases (clean source)
Huge amounts of energy released
Nuclear fuel is cheap and readily available
```
363
What are the cons of nuclear power?
Poor public perception
Hard to dispose of waste products
Risks of leaks
Overall cost is extremely high
