HP Definitions Flashcards
Refraction
The change in speed (with an associated change in wavelength) when a wave travels from one medium to another- if angle of incidence is greater than 0 there will be an associated change in direction
Refractive index
Measure of how much refraction occurs in a specific material
Critical angle
Angle of incidence of which the angle of refraction is equal to a right angle
EMF
Amount of energy given to each coulomb of charge as it passes through the supply
TPD
Voltage measured across the external load (and supply) when there is current in the circuit
Lost volts
Energy “lost” per coulomb of charge as it passes through the supply
A.C
Electrons changing direction many times per second
D.C
Electrons always move in the same direction
The R.M.S voltage of an A.C supply
is one which produces the same heating effect in a resistor as the equivalent D.C voltage
Resistance
Property of a material to oppose the flow
Internal resistance
Effective resistance that supply exhibits
Short circuit
When all external components are bypassed and a power supply is directly connected to itself. Effectively no resistance and current will become very high which can lead to battery heating up which is dangerous
Open circuit
No complete connection between positive and negative terminals of the power supply i.e switch opened
One condition which t.p.d = EMF
Conductor
Many free electrons
Insulator
Very few free electrons
Semiconductor
Very few electrons when pure but can conduct when impurities are present
Biasing a semiconductor
Applying a voltage to it
Diode
Component which only allows a current in one direction
LED
Light emitting diode
Pn junction is forward biased so electrons and holes move across junction and sometimes recombine at junction which releases energy in visible light
Colour depends on band gap of materials
Big band gap higher frequency
Projectile
Any moving object in free fall in a gravitational field
Oblique projectile
One where the launch angle is greater than 0 relative to the horizontal
3 conditions of projectile motion
- constant horizontal velocity
- constant vertical acceleration
- time of flight is the same for horizontal + vertical motion
- horizontal velocity is constant in magnitude and direction
- vertical velocity changes in magnitude and direction
Measuring acceleration
- release trolley
- use LG1 and card length to calculate initial velocity
- use LG2 to calculate final velocity
- record time between LG1 and LG2
- calculate acceleration using a=(v-u)/t
Photovoltaic effect
The production of electricity from light
Light energy shines on junction and photons absorbed and excite electrons from p-type valence band to jump to conduction band . These electrons then move to n-type and a charge can flow in an external circuit
Newtons first law
An object will remain at rest or travel in a straight line at constant velocity unless acted upon by an unbalance force
Newtons second law
Fun = ma
Terminal velocity
State of motion when an object is falling and no longer accelerates
Friction
Forces which acts against the motion of an object
Law of conservation of momentum
Total momentum before a collision is equal to total momentum after the collision IN THE ABSENCE OF EXTERNAL FORCES
Inelastic collision
One where kinetic energy after collision is not equal to the kinetic energy after
Objects stick together
Elastic collision
Kinetic energy is conserved and don’t stick together
Newtons third law
For every action there is an equal and opposite reaction
Doppler effect
Apparent change in the frequency of a wave caused by relative motion between source of wave and observer
Coherent waves
Same speed, frequency and wavelength + constant phase relationship
Interference
Property which defines wave motion
Path length
Shortest difference between source and maximum/minimum
Path difference
Mathematical difference between path lengths going to the same maximum/minimum
Irradiance
The power per unit area
(incident on a surface)
Intensity of a light source
Energy per second per unit area
Photoelectric effect
Removal of electrons from charged surfaces by photons of electromagnetic radiation
Work function
Minimum energy required to remove an electron from a particular metal with no kinetic energy
Threshold frequency
Minimum frequency of a photon required to remove an electron from a particular metal with no kinetic energy
Fermions
Particles which make up matter
Boson
Particles which give rise to forces
Proton
2 up quarks + 1 down quark
Neutron
1 up quark + 2 down quarks
Anti matter
- same mass
- opposite charge
- line across top of symbol
Evidence of neutrino
Beta decay
During beta decay the predicted energy didn’t add up and so electron must be sharing kinetic energy
Beta decay
Radioactive process which nucleus emits electron and neutron converted to proton
Nuclear fission
Large nucleus splits into smaller nuclei and releases energy and neutrons
Nuclear fusion
2 smaller nuclei combine to form a large nucleus which releases energy and neutrons
Energy level
Any of the energy states that the electron can occupy and still be associated with that atom. The electron can change energy level but cannot exist in an intermediate state between them.
Ground state
The lowest possible energy level that the electron can occupy. An entirely unexcited electron will occupy the ground state
Ionisation
An electron which is given enough energy that it can escape the atom will cause the atom to be ionised, without the electron it is no longer neutral and has become an ion. This process is known as ionisation.
