Higher Physics Whole Course Flashcards
Name the four Bosons.
- Photons
- W and Z Bosons
- Gluons
- Gravitons
How are absorption lines in the Sun produced?
Photons of certain frequencies are absorbed by the gases in the outer atmosphere of the Sun.
What is meant by fission?
Fission is when a nucleus of a large mass number splits into two or more nuclei of smaller mass numbers.
What is the critical angle?
The angle of incidence (within a material) that gives an angle of refraction of ninety degrees.
What quantity is always conserved in a collision?
Momentum
What is Newtons First Law?
If balanced forces act on an object it will : Remain at rest or continue to travel at a constant velocity in a straight line
What is the terminal potential difference, Vtpd?
It is the potential difference which is able to supply the user when the circuit is complete and current flows.
What is meant by 1 Farad?
1 Coulomb of charge stored per volt
What is 1 volt?
1 Joule of energy transferred per Coulomb of charge
When calculating power should you use Vpeak or Vrms?
Vrms
What is a coherent source?
Waves that have a constant phase difference (and the same frequency, wavelength and velocity)
How can an elastic collision be identified?
Calculate the total kinetic energy before the collision and the total energy after the collision.
If the total kinetic energy before the collision is equal to the total kinetic energy after the collision then it is an elastic collision.
What is the definition for 1 Newton?
One newton is defined as the force required to make a 1kg object accelerate at 1ms-2.
What would happen to your apparent weight if you were standing on a set of Newton scales and were in a lift that was de-accelerating downwards?
Your apparent weight would increase, It would be equal to your weight plus the force to cause the de-acceleration downwards.
In which mode is this operating?
Photoconductive
What is meant by fusion?
Fusion is when two small mass number nuclei combine to form a nucleus of a larger mass number.
Are all photons produced by energy level transitions visible?
No, some frequencies of photons may be in in the ultraviolet or X-ray frequency
What force is carried by a Graviton?
Gravity force
What force is carried by a Gluon?
Strong force
What is the definition for current?
Current is the number of Coulombs of charge passing a point in one second.
What is calculated from the area under a velocity - time graph?
Displacement
Give an example of a Baryon.
Proton
Neutron
What is potential difference?
The number of Joules of energy transferred per Coulomb of charge.
From the graph, how can you calculate the internal resistance of the cell?
internal resistance = - gradient
What is a point source?
This is a source where the light spreads evely in all directions
What is the difference between distance and displacement?
Distance is the length of the actual path travelled, Displacement is the straight line distance between where you started and where you finished, with a direction.
If an incident photon is greater than the work function what happens to the rest of the photon’s energy?
The electron that is ejected has the rest of the energy as kinetic energy.
What are the lost volts, Vlost?
This is the potential difference unavailable to the user because of the internal resistance of the supply.
Explain how an object reaches it’s terminal velocity.
The weight of the object acts down towards the surface of the planet. As the object falls it accelerates, as it does this the air resistance up the way will increase as it falls faster. Eventually the weight = air resistance. This gives equal and opposite forces so the forces are balanced. This gives a constant velocity, terminal velocity.
In the following circuit what quantity will the voltmeter measure and why?
The EMF as NO current is flowing as the circuit is incomplete.
What happens to the source frequency during the Doppler Effect?
Nothing - it remains constant
What is the wavelength of a wave?
Wavelength is the distance from a point on one wave to the same point on the next wave.
When will total internal reflection occur?
- Incident light must arrive at the boundary at an angle greater than the critical angle
- Occurs when light tries to pass from an optically dense material to a less dense material (e.g. from glass to air)
What are the advantages of using a grating to produce an interference pattern instead of a double slit?
- Fringes are brighter
- Fringes are sharper
What is the Work Function?
The minimum energy required to eject an electron from a metal surface.
Explain why an LED may not produce light EVEN when it is forward biased and connected to a supply voltage.
- The electrons in the n-type conduction band are not provided with enough energy to move into the conduction band of the p-type.
In the Gravitational Force equation what is the distance, r?
The distance, r, between the two objects is the distance between their centres of mass.
How can you increase the spacing between the maxima in am interference pattern created using a laser and a grating?
- Decrease the separation of the sources (more lines per mm)
- Increase the wavelength of the waves (Use a laser with a longer wavelength)
- Increase the distance between the sources and screen/detector
Explain why a reverse biased p-n junction will not conduct.
- Energy is supplied to the p-type material by the battery.
- This increases the internal electric field strength.
- The electrons in the conduction band of the n-type do not have enough energy to overcome the larger potential difference of the electric field.
- Electrons cannot pass into the conduction band of the p-type so the p-n junction will not conduct.
If an unstable nucleus undergoes beta decay what is given out and what is the effect on the mass number and the atomic number?
An electron from the nucleus is given out along with an antineutrino.
The mass number of the product remains the same and the atomic number increases by one.
What is your weight in freefall?
0 Newtons
When will time dilation become apparent?
The stationary observer and a person or object moving at relativistic speeds experience time passing in the same way. Only when they compare the times they have experienced do they notice a difference. The person who is stationary will have experienced a longer time in comparison.
What is the evidence for dark matter?
The mass of a galaxy can be estimated by the orbital speed of the stars within it. From our estimations there is not enough mass to keep the galaxy together. Therefore there must be mass we cannot detect. This is dark matter.
What force is carried by a photon?
Electromagnetic Force
What represents a magnetic field coming ‘out of the page’?
A dot
How is a p-n junction connected in forward bias?
Connect n-type to negative of supply connect p-type to positive of supply
What is the definition for time dilation?
Time dilation is the difference in a time interval as measured by an object moving relative to a stationary observer.
What two principles underpin the theory of relativity?
- When two observers are moving at constant speeds relative to one another, they will observe the same laws of physics.
- The speed of light (in a vacuum) is the same for all observers.
In the photoelectric effect, what happens to the maximum kinetic energy of an electron if the irradiance is increased?
Why?
- There is no effect on the maximum kinetic energy it remains the same.
- The energy of the incident photons (E = hf) is unchanged.
Explain how Hubble’s Law can estimate the age of universe.
Hubble’s observations show galaxies move away from each other and Earth in all directions. So the universe must be expanding. So if you could go back in time the galaxies etc. would be closer together, so if you go back to the point when all the galaxies were at one point, this would be the beginning of the universe. t=1/H0
How can an inelastic collision be identified?
Calculate the total kinetic energy before the collision and the total energy after the collision.
If the total kinetic energy before the collision is greater than the total kinetic energy after the collision then it is an inelastic collision.
Explain what a stationary observer would notice if a car with a siren on it was moving towards them.
Each wave front is emitted closer to the observer than the previous wave. So each wave front reaches the observer in less time than the previous wave. This causes the number of wave fronts arriving at the observer per second to increase. So the frequency the observer experiences is increased.
If a spectral line is bright - what does this tell you?
More electrons are making that energy level transition producing more photons of light with the same frequency.
Explain why a forward biased p-n junction conducts.
- Energy is supplied to the n-type material by the battery
- The effect of this is to reduce the potential difference of the electric field.
- The electrons in the conduction band of the n-type now gain enough energy to overcome the internal electric field and pass into into the conduction band of the p-type.
- The p-n junction will conduct.
For Doppler Effect calculations you use the following formula.
Describe when you should use the + and when you should use the - in the equation.
Sound source moving towards observer USE - as less time for waves to reach observer. Sound source moving away from observer USE + as more time for waves to reach observer.
From this energy level diagram, what type of material is being represented?
Semiconductor
In the photoelectric effect, if the frequency of the incident radiation is increased what happens?
The electrons ejected will have more kinetic energy, if the frequency is greater than the threshold frequency.
What would happen to your apparent weight if you were standing on a set of Newton scales and were in a lift that was accelerating upwards?
Your apparent weight would increase, It would be equal to your weight plus the force to cause the acceleration upwards.
What would happen to your apparent weight if you were standing on a set of Newton scales and were in a lift that was accelerating downwards?
Your apparent weight would decrease, It would be equal to your weight minus the force to cause the acceleration downwards.
Using a grating how can you increase the spacing between the maxima?
- Use a grating with a smaller slit separation.
- Use a source with a greater wavelength of light
- Move the screen further away
What are the main features of the Bohr model of the atom?
- Positively charged central nucleus.
- Electrons (negatively charged) are in discrete energy levels and do not radiate energy
- When an electron makes a transition from one energy level to another a specific amount of energy is lost or gained
- Each line in a spectrum is produced when an electron moves from one energy level to another.
What is the energy of the ionisation level?
0 Joules
Does a particle accelerator use a.c. or d.c. to create the electric field?
Explain why.
a.c.
This is because the electric field must change direction every time a particle completes a half circle (Dee) to keep the accelerating potential in the correct direction for the particles motion.
What 2 conditions are required for nuclear fusion?
- High Temperatures
- High Pressure
Explain how a pure semiconductor conducts.
Conduction band is empty. Valence band is full. There is a small energy gap. If the temperature is increased the electrons in the valence band can gain enough energy to jump the gap into the conduction band. These electrons are free to move and so conduction increases.
In the equation E = mc2 , what does the m stand for?
The mass which is converted into energy, which is the difference in mass of the particles before the fission/fusion reaction and the mass after.
What is the definition for Conservation of energy?
Energy cannot be created or destroyed, only converted from one form to another.
Why does the photoelectric effect give evidence for light to be considered as a particle?
- Photoelectric effect cannot be explained if light is thought of as a wave or any light would cause photoemission if it shone on the surface long enough to deliver enough energy to the electrons..
- Each photon contains a discrete amount of energy which results in one photon ejecting one electron
How is a p-n junction connected in reverse bias?
Connect n-type to positive of supply Connect p-type to negative of supply
What is the definition for redshift?
Redshift of light - Light from stars or galaxies moving away from us is shifted to longer wavelengths and so the redder wavelengths of the spectrum.
What is the difference between a vector and a scalar?
Scalar requires size / magnitude only Vector requires size / magnitude and a direction
Describe the electric field around a positive charge.
Field lines away from the positive charge.
What is calculated from the area under a speed-time graph?
Distance travelled
A triangular prism can be used to split white light into a spectrum. Why does this occur?
Different frequencies/colours have different refractive indices.
Why is the abundance of helium and hydrogen in the universe evidence for the Big Bang?
Big Bang Theory says that matter started as a very simple form that became more complex as time passed. The simplest elements would have formed first and existed in larger quantities than heavier elements, which would not exist until stars are born. These first elements were hydrogen and helium. The fact that there is an abundance of these elements in the universe supports the theory.
Explain what happens to the reading on the voltmeter when the circuit is changed from figure 1 to figure 2.
Resistance in the circuit decreases.
Current in the circuit increases.
Lost volts will increase Vlost = Ir
E - Vlost = Vtpd
So the reading on the voltmeter will decrease as it measures the Vtpd.
What will increase the amount of diffraction?
- Longer wavelengths diffract more
- Narrower gaps cause more diffraction
What type of spectrum is this?
Line emission spectrum
What could be altered in the circuit below to decrease the charging time of the capacitor?
- Decrease the resistance of the resistor
- Decrease the capacitance of the capacitor
What is meant by irradiance?
The power per unit area
Describe the shape of a graph of voltage across capacitor against time for discharging a capacitor.
Starts from the supply voltage Decreases to 0V.
What is meant by an ideal source?
A source which has no internal resistance.