G482 EXAM Definintions Flashcards

Question

Plane polarised wave

Answer 1

reference to a transverse wave or to vibrations in plane normal to the direction of (energy) propagation oscillations/vibrations in one direction only/confined to single plane (containing the direction of propagation)

Answer 2

I=I0 cos^2θ where I0 is the maximum intensity (of the polarised beam) when θ is zero maximum intensity transmitted/ image bright when θ is 90o minimum/zero intensity transmitted/image dim/vanished

Answer 3

a photon is absorbed by an electron (in a metal surface); causing electron to be emitted (from surface). Energy is conserved (in the interaction). Einstein's photoelectric energy equation... (energy of photon) = (work function of metal) + (maximum possible kinetic energy of emitted electron) work function energy is the minimum energy to release an electron from the surface Number of electrons emitted also depends on light intensity Emission is instantaneous

Answer 4

a quantum/lump/unit/packet/particle of (e-m) energy/light

Answer 5

all wavelengths/frequencies are present (in the radiation)

Answer 6

the average displacement/distance travelled of the electrons along the wire per second; (over time/on average) they move slowly in one direction through the metal/Cu lattice (when there is a p.d. across the wire) (because) they collide constantly/in a short distance with the lattice

Answer 7

λ distance between (neighbouring) identical points/points with same phase (on the wave) f number of waves passing a point /cycles/vibrations (at a point) per unit time/second v distance travelled by the wave (energy) per unit time/second

Answer 8

electrons have discrete energies in atom/AW each photon produced by electron moving between levels photon energy equal to energy difference between levels electron loses energy/making transition in correct direction

Answer 9

node occurs where the amplitude/displacement is (always) zero antinode occurs where the amplitude (of the standing wave) takes the only maximum (possible) value

Answer 10

A net flow of charged particles | I, measured in amps, the amount of electrical charge transferred per unit time (rate of flow of electrical charge)

Answer 11

Conventional-a model used to describe the movement of charged particles in a circuit. positive to negative Electron flow-the movement of electrons (charged particles) around a circuit. negative to positive

Answer 12

One coulomb is 1A x 1s. Unit of electrical charge 1.6x10^-19 C per electron

Answer 13

CONDUCTORS (metals) what makes them good conductors. INSULATORS (rubber, plastic) Have a much lower electron density (n) (≈ 10 9 m-3 = 1 mm-3). This means that there is only 1 electron which is free to move per mm3 and that is why insulators cannot conduct. SEMICONDUCTORS (silicon, germanium) Have an electron density (n) (≈ 10 19 m-3 = 10 10 mm-3) which lies between that of a conductor and an insulator. The value of n increases with increasing temperature, which means that it behaves as an insulator when it is cold and as a conductor when it is warm.

Answer 14

1V=1 joule per coulomb. Unit of potential difference and e.m.f.

Answer 15

E.m.f. (the voltage across an electrical source) is a voltage where Electrical energy is being transferred from the source to the charge. p.d. (the voltage across circuit components) is a Voltage where Electrical energy of the charge is being transferred to other energy forms in the circuit components.

Answer 16

a measure of opposition to the flow of charge (i.e. to electric current) caused by the repeated collisions between the charge carriers (usually electrons) in the material with each other and with the fixed positive ions of the material. It is measured in OHM (Ω)

Answer 17

A conductor has a resistance of 1 ohm (Ω) if the current in it is 1 ampere (A) when the pd across it is 1 volt (V).

Answer 18

If an external circuit is connected to the cell or battery, the reading on the voltmeter drops to a value less than E. when there is a current through the cell, some of its energy is converted into heat by the cell’s internal resistance. The decrease in voltage is called the ‘LOST VOLTS’ of the cell and it is proportional to the current. The reading (V) which is < E indicated by the voltmeter is the TERMINAL PD of the cell and also the pd across the resistor R.

Answer 19

The time taken for one complete pattern of oscillation in seconds

Answer 20

Waves rebound from a barrier, changing direction, remaining in the same medium (e.g. air)

Answer 21

When waves change direction, when they travel from one medium to another, due to a difference in the wave speed in each medium

Answer 22

Most of the solar UV incident on Earth is absorbed as it passes through the atmosphere about 98% of that which reaches ground level is UVA. The remaining 2% is mainly UVB since most of the UVC is absorbed by the ozone layer. UVA, B and C cause damage to collagen fibres in the skin which results in premature wrinkling and ageing of the skin. UVB induces the production of vitamin D in the skin, but it can cause sunburn and it can damage DNA in skin cells which may lead to skin cancer. High intensities of UVB can also lead to the formation of cataracts in the eyes. SUNSCREENS filter out or absorb UVB And so protect against sunburn and the Possibility of skin cancer. UV TYPE UVA (Long wave) UVB (medium wave) UVC WAVELENGTH RANGE A)320 nm to 400 nm B)280 nm to 320 nm C)100 nm to 280 nm

Answer 23

energy transferred from source/changed from some form to electrical energy; per unit charge (to drive charge round a complete circuit)