Physics Overall Flashcards
What are the two groups that fermions are broken down into
quarks and leptons
What are the six flavours of quark?
up down strange charm top bottom
What particles are in the leptons group?
electron muo tau as well as the neutrino counterpart of each
Name the 3 composite particles?
Hadron Baryon Meson
What is a hadron
a term used to describe any particle made of quarks. There are two basic types of hadron and these are Baryon and Mesons
What is a baryon
A subatomic particle made of three quarks. Examples include protons and neutrons
What is a meson
A subatomic particle made of two quarks (usually one quark and one anti quark)
list the two properties of a projectile
all projectiles have a constant acceleartion and a constat horizontal velocity
State the universal law of gravitation
there is a gravitational force between any two objects however it is usually negligible unless at least one of the objects is very large. The force of attractiona cts equally on both objects
Defintion of momentum
momentum is quite simply the product of mass and velocity for an object. It is a vectotr quantity
What is the principle of conversion of momentum
when objects collide(or explode apart) the total momentum of all the objects before the collision is equal to the total momentum of all the objects after the collision in the absence of external forces.
What are the four impluse equations?
ft = mv-mu = area under F-t graph = deltaP
What are the four impluse equations?
ft = mv-mu = area under F-t graph = deltaP
Define cosmic background radiation
it supports the big bang theory and is detected in all directions
If something is in redshift what does that mean in respect to you
it is moving away from you
Define dark energy
explanation for accelerating of the expansion of the universe
Define relativistic length contraction
A phenomenon observed when objects move at high velocity is that their length as measured by a “stationary” observer will appear to contract
Define constructive interference
constructive interference is when waves from two identical sources meet in phase. A detector placed in a position of constructive interference will detect a longer amplitude of wave.
Define destructive interference
destructive interference is when waces from two identical sources meet exactly out of phase(by half a wavelength.) A detector in this position will detect a smaller or even zero amplitude.
Explain why a person walking in front of two speakers will hear changes in the volume of sound when the amplitude of the speakers are constant
As they walk across the room they move through positions where the waves from the two sources meet in and out of phase. When they meet in phase a louder sound is heard due to construcitve interference. when they meet out of phase a quieter sound is heard due to destructive interference.
If Kinetic Energy is lost during a collison is it Elastic or Inelastic
Inelastic
If Kinetic Energy is gained during a collision is it Inelastic or Elastic
Elastic
What unit does Impulse have?
Ns(Newton,Seconds)
Define Dark Matter
makes galaxies spin too fast and you cant protect it easily
What are the four fundamental forces in the standard model?
Electromagnetic - Gravitational - Strong Nuclear Force - Weak Nuclear Force
Each Fundamental Force has a carrying particle - what is the broad name for these particles
boson
What is a Satellite in free fall around
A Planet/Star
What is the speed of light like in a vacuum in terms of all observers.
It is the same
What does the doppler effect cause
shifts in wavelengths of sound and light
What does the hubble-leimatre law allow us to do
Estimate the age of universe
how can we estimate the mass of a galaxy
the orbital speed of stars within it
What is the temperature of stellar objects related to
the distribution of emitted radiation over a wide range of wavelengths
What is redshift? in terms of wavelength
the change in wavelength divided by the emitted wavelength
What emits more radiation per unit surface area:
hotter objects or cooler objects
hotter objects
238
U. what is 92?
92
Atomic Number(the number of protons in the nucleus)
238
U. what is 238?
92
Mass Number (The total number of protons and neutrons in the nucleus)
What units is gravitational Field Strength measured in?
N kg - 1
What units is momentum measured in?
kg m s-1
What is the difference between a vector and a scalar?
Scalars have magnitude only, vectors have magnitude and direction
What is meant by a gravitational field strength of 6.7 N kg-1.
6.7 N of force acts on each kg of mass due to the gravitational field
What is meant by gravitational field strength?
the force applied per unit mass due to a gravitational field.
What is the force mediating particles associated with EM radiation?
photon
What is the standard name given to all particles made from quarks?
Hadrons
When drawing diagrams of electric field lines, will they point towards or away from a negative charge?
Towards
When drawing diagrams of electric field lines, will they point towards or away from a positive charge?
Away
In terms of sub atomic particles, what is an alpha particle?
2 protons and 2 neutrons
A radioisotope has an atomic number of 59. It then emits a beta particle. Its new atomic number will be
60
A radioisotope has an atomic number of 74. It then emits an alpha particle. Its new atomic number will be
72
What is meant by the “threshold frequency” of a metal?
The minimum frequency a photon must have to cause the emission of an electron from a meal surface.
Which photon will have the highest energy, 400nm or 700nm?
400 nm
Describe in simple terms a fusion reaction.
Two smaller nuclei collide to form one large nucleus in a process releasing energy
Describe how E=mc2 is used in the analysis of nuclear reactions.
The mass before the reaction is greater than the mass after, the difference in mass is the quantity which has been converted into energy.
What is meant by the work function of a metal?
The minimum energy a photon must have to cause the emission of an electron from a meal surface.
What is meant by total internal reflection?
When light strikes the inside surface of a material at a large enough angle (larger than critical angle) so that all of the light is internally reflected.
What is meant by critical angle?
The minimal angle of incidence at which total internal relection will take place in a material.
Will the wavelength of light in glass be larger or smaller than the same light in air?
Smaller
A particle travels horizontally underneath a negatively charged plate and above a positively charged plate and deflects upward. What could this particle be?
Any positively charged particle
What units is irradiance measured in?
W m-2
An electron in an atom falls from a high energy level to a lower energy level. What will happen?
A photon will be emitted.
What is meant by the “critical angle” for a material?
The minimum angle of incidence for which total internal reflection will take place.
Describe what is meant by the work function of a metal.
Minimum photon energy required to cause emission of an electron.
What is the approximate age of the universe?
13.8 billion years
In an experiment, what is the advantage of taking the same measurement many times?
Reduces the approximate random uncertainty
When white light is directed through a diffraction grating, what colour is the central maximum?
White
When white light is directed through a diffraction grating, what colour is deflected by a greater angle at the first maximum?
Red
What is the vertical velocity of a projectile at its maximum height?
0
Explain why the photoelectric effect provides evidence for the particle
nature of light
Each photon removes one electron.
It has been discovered that the rate of expansion of the universe is increasing.
State what physicists think is responsible for this increase.
Dark energy
If a stationary observer measures the length of s spaceship moving at 0.97c, how will his measurement compare to someone moving at the same speed as the spaceship?
shorter
What is evidence for dark matter?
Galaxies are spinning too quickly to be explained by matter alone.
What evidence supports the big bang theory?
Cosmic Microwave Background Radiation /
Name three types of lepton?
Tau, Electron, Muon (or their nutrinos or anti-particles)
What is the evidence for dark energy?
Accelerating expansion of the universe
If the kinetic energy after a collision is less than the kinetic energy before the collision, what type of collision is this?
inelastic
Describe the forces acting on an object moving at terminal velocity.
Frictional force and weight are balanced
What is Newton’s first law of motion?
An object will continue moving at a constant speed in a straight line unless acted upon by an unbalanced force.
What is the formula for the component of weight of an object acting down a slope?
F = m g sin θ
State the principle of conservation of energy.
Energy cannot be created or destroyed, only transferred from one form to another.
What is meant by an elastic collision between two objects?
Both momentum and kinetic energy will be conserved (the same before and after the collision)
What does it mean if a collision between two objects is described as inelastic?
Momentum will be conserved, but kinetic energy will be lost during the collision.
What is given by the area under a force time graph?
Impulse
Why is the light from most galaxies red-shifted?
Most galaxies are moving away from ours due to the expansion of the universe.
If a star is red in colour, is it hot or cold (for a star)?
cold
If starlight is blue in colour, describe the star’s temperature.
very high
The peak wavelength emitted by a star gives and indication of what?
temperature
What is meant by a potential difference of 2000 volts?
2000 J of energy given to each coloumb of charge
What is meant by a potential difference of 2000 volts?
2000 J of energy given to each coloumb of charge
Explain how your hand can be used to work out the direction of the force on a charged particle moving in a magnetic field.
Right hand positive, fingers= mag field, thumb= direction of motion of charge, palm=direction of force on particle
What happens if a positron and an electron collide?
the annihalate each other resulting in a release of energy according to E=mc2
Beta decay is evidence for which standard model particle?
Nutrino
What is the difference between spontaneous and induced nuclear fission?
Induced fission is initiated by another particle (e.g. a neutron). Spontaneous fission happens without cause (e.g. alpa decay)
How are engineers containing the high temperature plasma generated by a fusion reactor?
Particles contained by magnetic fields
If I move twice as far away from a point source of light, the irradiance will drop by a factor of…
4
State one experimental example of the particle nature of light.
Photoelectric effect
State one experimental example of the wave nature of electrons.
Electron diffraction
What is more likely to cause photo-electric emission, high irradiance red light or low irradiance blue light?
blue light as photons have more energy
What does it mean if two waves are described as coherent?
they have a constant phase relationship
What happens to the wavelength of light as it moves from air into glass?
wavelength decreases
What happens to the wavelength of light as it moves from glass into air?
wavelength increases
What happens to the frequency of light as it moves from air into glass?
does not change
What happens to the velocity of light as it moves from air into glass?
velocity decreases
State the law of conservation of linear momentum
Total momentum before a collision is equal to the total momentum after a collision
in the absence of external forces
State two features of the Bohr model of the atom.
A (central) positively charged nucleus.
Explain what is meant by the term fundamental particle
Fundamental particles are not
composed of other particles.
when the potential difference across a capacitor is 1 farad, how much coulombs of charge does it store
1 coulomb of ch
State the effect that doping has on the conducitivty of silicon
increased conductivity
Using band theory, explain why conduction take place in a semi-conductor at room temperature
The band gap between the valence and conduction band is small.
Some electrons have enough energy to move from the valence to the conduction band.
How do you verify the inverse sqaure law for a point source of light
obtain values of irradiance
plot graph of I against 1/d2
Graph is straight line through the origin
Define the Valence Band
The highest energy band where electrons normally reside
Define Conduction Band
The energy band abige the valence band
In a conductor, what is happening with thr valence and conduction bands
They overlap which means that electrons can move freely between the bands and through the material so electrons can flow and the materials conduct electricity.
In an insulator, what is hapoening in terms of the valence and conduction bands
The Valence and Conduction band are seperated by a large ‘band gap’.
In a semi-conductor, what is happening with the valence and conduction bands
There is a small band gap
What impact does doping have?
Improves performance by lowering resistance
How does doping work?
Adds charge carriers which lowers resistance
What is the definition of alternating current
Where the current changes directions many times per second
What is meant by an e.m.f of 9V?
9 Joules of energy are given to each coulomb of charge that passes through the cell.
How do you calculate the internal resistance when you have access to a graph with V(E.M.F) plotted against I(Short Circuit)
Get the -gradient of the straight line
What is a capacitor
A capacitor is a device which stores electrical charge.
The amount of charge it can store is dependent on its capacitance (measured in farads) and the voltage to which it is charged.
Silicon and other semi-conductors can be doped to form….
P-type and n-type semi-conductors
Describe LED Theory
Electrons fall from conduction band of n-type to valence band of p-type. This results in the emission of a photon.
A potential difference is produced when photons enter the layer between the p-type and n-type materials. State the name of this effect.
Photovoltaic Effect
What is the formula for lost volts
Ir
List all the formulas for electricity etc
E = V + Ir E = IR + Ir E= V + Vlost E = IR + Vlost V = IR Vlost = Ir E = I(R + r)
Electrical charges ______ and opposite charges _____
Repel and attract
What do field lines show
The direction of the force experienced by a positive charge
If field lines are closer together what does that
The field is stronger
name the most famous particle accelerator
LHC
What are particle accelerators used for
Accelerators use electric fields to contain and accelerate charged particles to very high speed.
In terms of magnetic forces, what hand is positive?
Right
What are the two groups that fermions are broken down into
quarks and leptons
What is a meson
A subatomic particle made of two quarks (usually one quark and one anti quark)
Define Nuclear Fission
A single large nucleus is split producing two smaller nuclei and neutrons in a process that releases energy
Define Nuclear Fusion
Two small nuclei are fused together to produce a larger nucles
When does refraction of light happen?
When light moves from one medium to another
What is the refractive index of air and vacuum
1.0
When will total internal reflection occur?
When the angle of incidence inside the material is attempting to leave and it is greater than the critical angle.
Define interference
A property exhibited by waves and is considered a test for whether something is actually a wave at all
What are diffraction grating used for?
To cause intereference in patterns in light
What is a photon?
Force mediating particle which is a small bundle of energy
What do you call the minimum energy requirement to eject an electron
The work function
What do you call the minimum frequency requirement to eject an electron
Threshold frequency
What happens if the incident photon contains more energy than the work function?
The excess energy is given to the ejected electron in the form of kinetic energy
In terms of the photoelectric effect, does the plate need to be negatively or positively charged?
Negatively charged
Define Irradiance
Power per unit area
Magnetic fields are used to contain the plasma inside the fusion reactor.
Explain why it is necessary to use a magnetic field to contain the plasma.
Plasma would cool down if it came
too close to the sides (and reaction
would stop)
Methods to improve an irradiance experiment
Black cloth to reduce reflections
Explain how dark lines in the spectrum of sunlight are produced.
photons of particular frequencies are absorbed in the suns upper atmosphere
State two features of the Bohr Model of the Atom
A central positively charged nucleus
