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OCR - AS physics Unit 2 - Electrons waves and Photons
for all of you AS students who are thourouhly terrible at physics and need a bit of a nudge in the right direction like me
47
Physics
Not Applicable
01/16/2014

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Term
Define a Coulomb
Definition
quantity of charge which passes when a current of 1 ampere passes for a time of 1 second
Term
What is the value of the elementary charge?
Definition
1.6 x 10^-19
Term
State Ohm's Law
Definition
At constant temperature, the voltage of a conductor is directly proportional to it's current
Term
Define Charge
Definition
Current x time
Term
Define Current along with it's formula (2 points)
Definition
Rate of flow of charge
Q = I * t
Term
Define Ampere
Definition
The fundamental SI unit of Current
Term
State Kirchhoff's first law, and is a consequence of ____
Definition
the sum of current entering a junction is equal to the sum of currents leaving a junction
-consequence of conversion of charge
Term
State Kirchhoff's second law, and is a consequence of ____
Definition
In any closed circuit, the sum of all p.d.s is equal to the sum of all e.m.f.s
-consequence of conservation of charge
Term
Define resistance
Definition
property of a component that regulates the electrical current though it
measured in ohms
Term
Define Electromotive force
Definition
is the energy transferred per unit charge when one type of energy is converted into another form of energy
Term
Define Potential difference
Definition
is the energy transferred per unit charge when electrical energy is converted into another form of energy
Term
Define Resistivity
Definition
is defined as p= RA / l
where;
p= resistivity
R= cross sectional area
A= cross sectional area
l= length of wire
Term
Define Internal resistance
Definition
resistance of an e.m.f. source (due to the chemicals in the cell or battery)
Term
Define terminal p.d.
Definition
total p.d. across the load external resistance
Term
I-V characteristic of a LED
Definition
- near infinite resistance before 0.6 V
- resistance decreases as voltage increases after 0.6 V
Term
I-V characteristic of a Filament lamp
Definition
Resistance is proportional to voltage until it reaches 1.5 V wherein the resistance increases as the Temperature increases
Term
I-V characteristic of a fixed resistor
Definition
straight diagonal line that goes through the origin
Term
Define Power
Definition
Rate at which work is done
Term
Unit of:
a. power
b. energy
Definition
a. watts
b. joules
Term
Define a progressive wave
Definition
waves that move away from a source
Term
Define transverse waves
Definition
the direction of oscillation is perpendicular to the direction of propagation
Term
Define longitudinal wave
Definition
direction of oscillation is parallel to the direction of propagation
Term
Define Displacement
Definition
distance from a point in the wave to the mean value
Term
Define Amplitude
Definition
maximum displacement from the mean
Term
Define Frequency
Definition
the amount of complete oscillations within a given unit of time
Term
Define wavelength
Definition
smallest distance between one point on a wave and the identical point on the next wave
Term
Define Period
Definition
Time taken to complete one full oscillation
Term
Define Phase difference
Definition
amount by which one oscillation lags/leads behind another measured in rads
Term
Relationship of INtensity and Amplitude
Definition
Intensity is directly proportional to amplitude^2
Term
Define Reflection
Definition
occurs when a wave bounces back from the surface of an obstacle
Term
Define Refraction
Definition
occurs when the wave enters a different medium with a higher density than air and changes direction and speed
Term
Define Diffraction
Definition
The spreading of waves when they pass though a aperture or around an object
Term
Define Polarisation
Definition
process of converting an unpolarised wave into a polarised wave
Term
How would you conduct a experiment to see the polarisation of microwaves (3 marks)
Definition
Two polarising filters placed between transmitter and receiver that are facing each other [1]. Start with both filters being parallel to each other, which allows microwaves through freely, then twist the second filter through 90 degrees and observe the drop in detection until 0 [1]. This shows that the microwaves must have been polarised through the first filter, otherwise detection would have been equal throughout the rotation. [1]
Term
Describe Malus's law
Definition
A physical law that describes the cgane in intensity of a wave passing though a polaroid analyser
Term
Define Interference
Definition
the superposition of 2 or more waves that result in a new wave pattern
Term
How can a wave be coherent?
Definition
coherent waves arewaves that have the same frequency and a constant phase difference
Term
Constructive interference
Definition
occurs when two waves that are in phase reinforce
Term
destructive interference
Definition
occurs when two waves that are antiphase cancel each other out
Term
Define monochromatic
Definition
Light that has the same wavelength
Term
How is a stationary wave formed?
Definition
A stationary wave is formed when two coherent waves that are travelling in opposite directions superpose
Term
what is a node?
Definition
a node is a spot where the displacement is always zero due to destructive interference
Term
What is an antinode
Definition
an antinode is a spot where the amplitude is maximum due to constructive intereference
Term
Define Threshold frequency
Definition
Frequency of elctromagnetic radiation that will result in an emmision of photoelectrons from a specified metal surface
Term
Define Electron volt
Definition
Energy charge of an electron as it moves through a potential difference of 1 volt
Term
Define Work function
Definition
energy required to move an electron from it's surface
Term
Stopping potential
Definition
The Potential difference required to stop the movement of electrons in a closed circuit
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