aqa a level physics paper 1
What is meant by work function (2) - Answers -Minimum energy required by an electron
to escape from (1) a metal surface (1)
What is meant by ionisation energy? (2) - Answers -Minimum energy required to
remove an electron from an atom (1) from the ground state (1)
Why do emitted electrons have a kinetic energy that varies up to a maximum value? (4)
- Answers -Energy of a photon is fixed/constant (1)
Energy is required for electrons to overcome work function ø (1)
Electrons deeper into/below the surface of the metal require more energy to overcome
work function and therefore have less KE(1)
Maximum KE = Energy of photon - work function ø (1)
Explain how (bright ring) diagram is evidence of the wave-particle duality of electrons? -
Answers -Diffraction pattern maxima/minima (bright and dark areas) (1)
Diffraction is a property of waves- proves wave-behaviour of electrons (1)
What is meant by the ground state? - Answers -The lowest energy state of an atom
Explain the difference between excitation and ionisation (2) - Answers -An electron
receives a discrete amount of energy for BOTH (1)
Excitation promotes an electron to a higher energy level
Ionisation is when an electron receives enough energy to leave the atom
Explain why only photons of certain frequencies cause excitation (4) - Answers -discrete
energy levels (1)
Electrons need to absorb a DISCRETE amount of energy to move to a higher energy
level (1)
Photons need to have a certain frequency to provide this energy, because E=hf (1)
interaction is a 1:1 reaction all of the photon's energy is absorbed (1)
Explain how excitation takes place in a fluorescent tube - Answers -Electrons flow
through the tube to the applied PD causing a current to flow (1)
Electrons collide with mercury atoms in the tube (1)
This raises electrons in the mercury atom to a higher energy level (1)
What is the purpose of coating in a fluorescent tube? - Answers -UV/ High energy
photons emitted from mercury atoms when the electrons in the atom de-excite (1)
High energy photons absorbed by the coating (1)
Coating emits photons in the visible spectrum (1)
, What happens when annihilation occurs? (2) - Answers -particle and an anti-particle
collide and cease to exist (1)
Their mass is released as energy in the form of a pair of gamma photons (1)
How does the strong nuclear force between two nucleons vary with the separation of
the nucleons? (3) - Answers -repulsive at < 0.5 fm (1)
attractive from 0.5 to 3 fm (1)
above 3 fm, force 0 (1)
What is meant by monochromatic light - Answers -light of a single frequency
What is meant by coherent - Answers -constant phase difference
Effect on diffraction pattern when wavelength decreases (3) - Answers -Maxima closer
together (1) angle decreases (1) smaller path difference (1)
What happens when white light is used in slits instead of monochromatic light? (4) -
Answers -Central bright fringe (maximum) is white (1)
Fringes on either side are continuous spectra (1)
Dark fringes would be closer together due to λred being larger than the average λwhite
(1)
Bright fringes (maxima) are wider
How do diffraction patterns (fringes on the screen) form? - Answers -Interference (1)
from light from two slits overlapping (superposition) (1)
maxima where crests meet (constructive interference) (1)
dark fringes/minima form where crest and trough meet (destructive interference) (1)
Formation of a stationary wave - Answers -Two waves superpose (1)
same wavelength and/or frequency (1)
Travelling with equal and opposite velocity (direction of movement) (1)
stationary vs progressive waves (3 for each) - Answers -stationary: have
nodes/antinodes (1) points between nodes all in phase (1) cannot transfer energy
progressive: no nodes/antinodes (1) within one wavelength all points are out of phase
(1) can transfer energy
How does TIR transmit information in an optical fibre? (2+ diagram) - Answers -Core
has higher refractive index than cladding (1) when incident light at a greater angle than
critical angle of cladding TIR occurs (2)
Observations of a polarisation filter rotation? ("What observations could be made when
the filter in rotated through 360˚?") - Answers -Variation in intensity between maxima
and minima (light and dark) (1)
Two maxima and Two minima within 360 (1)
What is meant by work function (2) - Answers -Minimum energy required by an electron
to escape from (1) a metal surface (1)
What is meant by ionisation energy? (2) - Answers -Minimum energy required to
remove an electron from an atom (1) from the ground state (1)
Why do emitted electrons have a kinetic energy that varies up to a maximum value? (4)
- Answers -Energy of a photon is fixed/constant (1)
Energy is required for electrons to overcome work function ø (1)
Electrons deeper into/below the surface of the metal require more energy to overcome
work function and therefore have less KE(1)
Maximum KE = Energy of photon - work function ø (1)
Explain how (bright ring) diagram is evidence of the wave-particle duality of electrons? -
Answers -Diffraction pattern maxima/minima (bright and dark areas) (1)
Diffraction is a property of waves- proves wave-behaviour of electrons (1)
What is meant by the ground state? - Answers -The lowest energy state of an atom
Explain the difference between excitation and ionisation (2) - Answers -An electron
receives a discrete amount of energy for BOTH (1)
Excitation promotes an electron to a higher energy level
Ionisation is when an electron receives enough energy to leave the atom
Explain why only photons of certain frequencies cause excitation (4) - Answers -discrete
energy levels (1)
Electrons need to absorb a DISCRETE amount of energy to move to a higher energy
level (1)
Photons need to have a certain frequency to provide this energy, because E=hf (1)
interaction is a 1:1 reaction all of the photon's energy is absorbed (1)
Explain how excitation takes place in a fluorescent tube - Answers -Electrons flow
through the tube to the applied PD causing a current to flow (1)
Electrons collide with mercury atoms in the tube (1)
This raises electrons in the mercury atom to a higher energy level (1)
What is the purpose of coating in a fluorescent tube? - Answers -UV/ High energy
photons emitted from mercury atoms when the electrons in the atom de-excite (1)
High energy photons absorbed by the coating (1)
Coating emits photons in the visible spectrum (1)
, What happens when annihilation occurs? (2) - Answers -particle and an anti-particle
collide and cease to exist (1)
Their mass is released as energy in the form of a pair of gamma photons (1)
How does the strong nuclear force between two nucleons vary with the separation of
the nucleons? (3) - Answers -repulsive at < 0.5 fm (1)
attractive from 0.5 to 3 fm (1)
above 3 fm, force 0 (1)
What is meant by monochromatic light - Answers -light of a single frequency
What is meant by coherent - Answers -constant phase difference
Effect on diffraction pattern when wavelength decreases (3) - Answers -Maxima closer
together (1) angle decreases (1) smaller path difference (1)
What happens when white light is used in slits instead of monochromatic light? (4) -
Answers -Central bright fringe (maximum) is white (1)
Fringes on either side are continuous spectra (1)
Dark fringes would be closer together due to λred being larger than the average λwhite
(1)
Bright fringes (maxima) are wider
How do diffraction patterns (fringes on the screen) form? - Answers -Interference (1)
from light from two slits overlapping (superposition) (1)
maxima where crests meet (constructive interference) (1)
dark fringes/minima form where crest and trough meet (destructive interference) (1)
Formation of a stationary wave - Answers -Two waves superpose (1)
same wavelength and/or frequency (1)
Travelling with equal and opposite velocity (direction of movement) (1)
stationary vs progressive waves (3 for each) - Answers -stationary: have
nodes/antinodes (1) points between nodes all in phase (1) cannot transfer energy
progressive: no nodes/antinodes (1) within one wavelength all points are out of phase
(1) can transfer energy
How does TIR transmit information in an optical fibre? (2+ diagram) - Answers -Core
has higher refractive index than cladding (1) when incident light at a greater angle than
critical angle of cladding TIR occurs (2)
Observations of a polarisation filter rotation? ("What observations could be made when
the filter in rotated through 360˚?") - Answers -Variation in intensity between maxima
and minima (light and dark) (1)
Two maxima and Two minima within 360 (1)
