A level Physics OCR A Paper 2
Study
Difference between stationary and progressive waves
A progressive wave transfers energy, all parts of its wave have the same amplitude
Mean drift velocity
The average displacement of electrons as they move along a wire per second
On average, they travel more slowly in one direction through the metal lattice due to
collisions with it
Number density of conductors, insulators and semiconductors
Conductors - 10^29
Semiconductors - 10^19
Insulators - 10^9
Potential difference
Energy transferred from electrical to other forms per unit charge
EMF
The work done transferred from other forms to electrical per unit charge
Ohm's Law
At a constant temperature, the current is directly proportional to the voltage.
How does the resistivity of a metal vary with temperature?
Resistivity increases with an increase in temperature as the thermal velocity of the free
electrons increases and hence the number of collisions between free electrons also
increases.
Kirchhoff's Second Law
The total emf around a loop = the sum of p.d.s across each component. (Conservation
of energy)
How does the resistivity of a semiconductor vary with temperature?
The resistivity decreased with an increase in temperature as more electrons jump into
the conduction band, increasing its conductivity
Internal resistance
The resistance of a source of emf due, caused by thermal energy transfer, which
causes a loss in voltage as charge passes through the sourcef
V-I graphs
y-intercept: emf
gradient = -r
(max P when R=r?)
I-V graph thermistor
Resistance decreases with increase in temperature
reflect filament graph in y=x
Resistance-Intensity graph of an LDR
Resistance decreases with light intensity increase
Rational function graph
Time period
The time taken for one complete oscillation/cycle to pass a point
Refraction
, The bending of a wave (change in direction) as it enters a new medium at an angle
Slowing down - towards normal
Speeding up- away from normal
FAST
Polarisation
The phenomenon in which oscillations of a transverse wave are limited to only one
plane
Total internal reflection
The complete reflection of light hitting a boundary between two media back into it'd
original medium (with a higher refractive index) when the incidence angle>critical angle
Critical angle
An angle of incidence that results in an angle of refraction of exactly 90 degrees (when
the refracted ray travels along the boundary line)
Principal of superposition
Whenever two+ waves pass through each other, the resultant displacement is the sum
of all the individual displacements occuring at that point
Path difference
The difference in the distance travelled by two waves from the source to a specific point
Phase difference
The difference between two points on a wave. Expressed in radians
Stationary waves
A wave pattern with nodes and antinodes formed when two or more progressive waves
of the same frequency and amplitude pass through each other.
Harmonics
Multiples of the fundamental frequency
Fundamental frequency
The lowest frequency of vibration (of a standing wave)
How are pd and emf different?
emf - from other to electrical
pd - from electrical to other
What are lost volts?
'Lost volts' refer to the difference in voltage between that supplied by the source and the
amount available to the circuit.
They are 'lost' due to the internal resistance of the source.
emf - pd
Wavelength
The distance between two adjacent points of a wave when they're in phase
Intensity
The radiant power passing through a surface per unit area
I =P/A
I is directly proportional to the amplitude squared
How can you demonstrate that a beam of light is polarised?
Study
Difference between stationary and progressive waves
A progressive wave transfers energy, all parts of its wave have the same amplitude
Mean drift velocity
The average displacement of electrons as they move along a wire per second
On average, they travel more slowly in one direction through the metal lattice due to
collisions with it
Number density of conductors, insulators and semiconductors
Conductors - 10^29
Semiconductors - 10^19
Insulators - 10^9
Potential difference
Energy transferred from electrical to other forms per unit charge
EMF
The work done transferred from other forms to electrical per unit charge
Ohm's Law
At a constant temperature, the current is directly proportional to the voltage.
How does the resistivity of a metal vary with temperature?
Resistivity increases with an increase in temperature as the thermal velocity of the free
electrons increases and hence the number of collisions between free electrons also
increases.
Kirchhoff's Second Law
The total emf around a loop = the sum of p.d.s across each component. (Conservation
of energy)
How does the resistivity of a semiconductor vary with temperature?
The resistivity decreased with an increase in temperature as more electrons jump into
the conduction band, increasing its conductivity
Internal resistance
The resistance of a source of emf due, caused by thermal energy transfer, which
causes a loss in voltage as charge passes through the sourcef
V-I graphs
y-intercept: emf
gradient = -r
(max P when R=r?)
I-V graph thermistor
Resistance decreases with increase in temperature
reflect filament graph in y=x
Resistance-Intensity graph of an LDR
Resistance decreases with light intensity increase
Rational function graph
Time period
The time taken for one complete oscillation/cycle to pass a point
Refraction
, The bending of a wave (change in direction) as it enters a new medium at an angle
Slowing down - towards normal
Speeding up- away from normal
FAST
Polarisation
The phenomenon in which oscillations of a transverse wave are limited to only one
plane
Total internal reflection
The complete reflection of light hitting a boundary between two media back into it'd
original medium (with a higher refractive index) when the incidence angle>critical angle
Critical angle
An angle of incidence that results in an angle of refraction of exactly 90 degrees (when
the refracted ray travels along the boundary line)
Principal of superposition
Whenever two+ waves pass through each other, the resultant displacement is the sum
of all the individual displacements occuring at that point
Path difference
The difference in the distance travelled by two waves from the source to a specific point
Phase difference
The difference between two points on a wave. Expressed in radians
Stationary waves
A wave pattern with nodes and antinodes formed when two or more progressive waves
of the same frequency and amplitude pass through each other.
Harmonics
Multiples of the fundamental frequency
Fundamental frequency
The lowest frequency of vibration (of a standing wave)
How are pd and emf different?
emf - from other to electrical
pd - from electrical to other
What are lost volts?
'Lost volts' refer to the difference in voltage between that supplied by the source and the
amount available to the circuit.
They are 'lost' due to the internal resistance of the source.
emf - pd
Wavelength
The distance between two adjacent points of a wave when they're in phase
Intensity
The radiant power passing through a surface per unit area
I =P/A
I is directly proportional to the amplitude squared
How can you demonstrate that a beam of light is polarised?
