HP Remember Flashcards
The thermistor is made of semiconductor material
Using band theory, explain why the conductivity of the thermistor increases as it is heated
The band gap between the valence and the conduction band in semiconductors is small
Giving electrons heat energy allows more per second to jump from the valence band to the conduction band
Light from sun is used to produce a visible spectrum
A student views this spectrum and observes a number of dark lines as shown
Explain how these dark lines in the spectrum of sunlight are produced
photons of particular/some/
certain energies/frequencies are
absorbed (1)
in its/the Sun’s (upper/outer)
atmosphere/outer layers (1)
Emission lines occur
at specific wavelengths which relate to the electron energy transitions
Explain how emission spectrum is then produced from this atom
Sometimes when electrons drop energy levels, photons are given off. The photons wavelength is dependent on band gap energy levels
This generates a spectra and each line represents the wavelength of a photon
Magnetic fields are used to contain 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
Why is energy released in fusion/fission?
Mass is converted into energy
Explain in terms of waves how a maximum is produced
Peaks meet in phase
Using band theory, explain how a potential difference is produced when photons of light are incident on the photodiode
Electrons gain/absorb energy from
photons/light (1)
Electrons move from valence band to
conduction band (1)
Electrons move towards n-type
semiconductor (producing a
potential difference). (1)
Particle composed of quark-antiquark pair
Meson
Pions have a mean lifetime of 26ns in their frame of reference
Explain why a greater number of pions are detected at the second detector than would be expected if relativistic effects are not taken into amount
For a stationary observer’s frame of
reference, the mean lifetime of the
pion is greater (than 26 ns)
OR
In a pion’s frame of reference, the
distance is shorter (than 30.0 m).
Explain why protons are accelerated by an electric field
Protons are (positively) charged (1)
Protons experience a force (in the
electric field) (1)
The train emits a beam of light towards the stationary observer
State the speed of the emitted light as measured by the stationary observer
Justify your answer
3x10^8
Speed of light is the same for all observers
Explain, in terms of energy band gaps, the difference between photons emitted by the red LEDs and photons emitted by the blue LEDs
The (energy) band gap in a blue LED
is greater. (1)
The photons of blue light have more
energy (than the photons of red
light). (1)
Why is an alternating voltage used in the cyclotron
To ensure electric field is always acting in correct direction
Describe an experiment to verify the inverse square law for a point source of light
Place the light detector a distance from the lamp. Measure the distance from the light detector to the lamp and the irradiance of the light at this distance. Repeat these measurements for different distances between detector and lamp. Plot a graph of light irradiance against 1/distance2 from the lamp.
One feature of the Bohr model of the hydrogen atom is that the electron can only occupy discrete energy levels
State one other feature of the Bohr model of the hydrogen atom
A (central) positively charged
nucleus.
OR
When an electron moves from one
state to another, the energy lost or
gained is done so ONLY in very
specific amounts of energy.
OR
Each line in a spectrum is produced
when an electron moves from one
energy level/orbit/shell to another.
Do not accept:
Atom is mainly empty space.
Nucleus is small compared to size of
atom.
Any statement referring to photons
and photon frequency is a
consequence, not a feature.
Explain how a line emission spectrum is produced
If an electron is in an excited state it
can return to a lower energy level.
When it does this, it emits a photon.
(1)
Different transitions produce
different lines/ frequencies (of
photons).
Explain why some lines on a line emission spectrum are brighter than others
(For the brighter lines) more
electrons are making those
transitions (per second).
(1)
(Therefore), there are more photons
(per second) emitted (of that
specific energy and so produce
brighter lines).
Explain why protons are accelerated by an electric field
Protons are (positively) charged (1)
Protons experience a force (in the
electric field) (1)
The student observes a second yellow spectral line at a wavelength of 589.6 nm
The student observes that the line at 589 nm is brighter than the line at 589/6 nm
Explain this observation
There are more electrons (per
second) making the transition for the
589.0 nm line. (1)
Meaning more photons (per second)
are emitted. (1)
OR
There are fewer electrons (per
second) making the transition for the
589.6 nm line. (1)
Meaning fewer photons (per second)
are emitted. (1)
Describe how this apparatus could be used to verify the inverse square law for a point source of light
Obtain values of irradiance for different distances (1)
Plot graph of I against 1/d^2
(1)
Graph of I against 1/d^2 is a straight line through the origin (then this verifies the inverse square law of
light) (1)
Explain why the reading on the voltmeter decreases when the switch is closed
Now current in circuit
So voltage can be lost to internal resistance
Describe a method to obtain an accurate value for the period T using only a stopwatch
Measure the total time over a
number of swings (1)
Divide total time by number of
swings (1)
Suggest an improvement to the experimental procedure that would allow a more previse value for the minimum period T to be determined
Use smaller increments around the
‘turning point’.
OR
Take more measurements about the
‘turning point’.
OR
Take more measurements over the
whole range.
State one way in which the experiment could be improved for calculating irradiance
Justify your answer
Smaller lamp
Will be more like a point source
Explain why a spectrum is produced in the glass prism
Different frequencies/ colours
have different refractive indices
(1)
or
Different frequencies/
colours are refracted through
different angles (1)
Suggest why connecting wires in a circuit would have a large diameter
(Wire of large diameter) has a low
resistance (1)
or
to prevent overheating (1)
or
to prevent wires melting (1)
Explain why charging current decreases as battery charges
The e.m.f. of the battery
increases (1)
Difference between the two e.m.f.s decreases (1)
Using the same apparatus, the student now wishes to determine more precisely the minimum angle of deviation
Suggest two improvements to the experimental procedure that would achieve this
Repeat measurements (1)
More measurements around/ close
to a minimum or smaller ‘steps’ in angle (1)
Why is energy released in a fusion reaction
Mass is converted into energy
One student states that the clocks on board the plane will run slower when plane is travelling at relativistic speeds
Explain whether or not this statement is correct
Correct – from the perspective of
the stationary observer there will be time dilation
A voltage is applied across an LED so that it is forward biased and emits light
Using band theory, explain how the LED emits light
(Voltage applied causes) electrons
to move towards conduction band of
p-type/ away from n-type (towards
the junction) (1)
Electrons move/ drop from
conduction band to valence band
(1)
Photon emitted (when electron
drops) (1)
