Rev: Phys 2

Front 1

CONVENTIONAL CURRENT VS ELECTRON FLOW

Back 1

current moves from + to – (of battery in circuit) and electrons move from – to +

Front 2

WHAT IS 230V, 25W

Back 2

When connected/using/AW to the 230 V supply
the power/energy per second from supply/output/dissipated/AW
is 25 W

Front 3

INTENSITY

Back 3

intensity is the (incident) energy per unit area per second

Front 4

EFFICIENCY

Back 4

efficiency = power out/power in

Front 5

ADVANTAGES OF DATA LOGGERS

Back 5

continuous record for very long time scale of observation
can record very short time scale signals (at intervals)
automatic recording/remote sensing
data can be fed directly to computer (for analysis)

Front 6

POLARISING WAVES

Back 6

emitted wave is (plane) polarised
detecting aerial will receive weaker signal/cos θ component
when it is rotated (through angle θ)/AW
signal falls to zero at 90
and then rises to max again at 180

Front 7

UV RADIATION

Back 7

UV-A causes tanning or skin ageing ; most of (99%) uv light;
400-315 nm
UV-B causes damage or sunburn or skin cancer; 315-260 nm
UV-C is filtered out by atmosphere/ozone layer; 260-100 nm

Front 8

WHY ELECTRONS CAN BE EMITTED FROM SURFACE WITH UV AND NOT WITH IR

Back 8

energy of the infra-red photon is less than
the work function of the metal surface

Front 9

LONGITUDINAL VS TRANSVERSE

Back 9

oscillation/vibration of particles/medium in direction of travel of the
wave
example: sound wave, etc.
oscillation/vibration of particles/medium (in the plane) at right
angles to direction of travel of the wave
example: surface water waves, string, electromagnetic, etc

Front 10

FORMATION OF STATIONARY WAVES

Back 10

the incident wave is reflected at the end of the pipe
reflected wave interferes/superposes with the incident wave
to produce (a resultant wave with) nodes and/or antinodes

Front 11

EXAMPLES OF EXPLAINING MOTION IN STATIONARY WAVES

Back 11

at 0 oscillation with max amplitude
along tube
at 0.2 m (oscillation along tube with) smaller amplitude
at 0.6 m no motion/node


oscillation at 3 times the frequency of c(i)
at 0 (oscillation with) max amplitude (along tube)/antinode
at 0.2 m no motion/node
at 0.4 m motion as at 0 (but in antiphase/opposite direction)

Front 12

LINE SPECTRUM

Back 12

light emitted from (excited isolated) atoms produces a line spectrum
a series of (sharp/bright/coloured) lines
against a dark background

Front 13

ABSORPTION VS EMISSION

Back 13

in an absorption spectrum a series of dark lines (appears against a
bright background/within a continuous spectrum)

Front 14

MEAN DRIFT VELOCITY

Back 14

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/AW

Front 15

LED GRAPH CHARACTERISTICS

Back 15

no current/no light/does not conduct until V is greater than 1.5 V
brightness/intensity of LED increases with current/voltage above 1.5 V
above 1.8 V current rises almost linearly with increase in p.d./AW
the LED does not obey Ohm’s law
as I is not proportional to V/AW
below 1.5 V, LED acts as an infinite R/ very high R/acts as open switch
above 1.5 V, LED resistance decreases (with increasing current/voltage)

Front 16

WHY RESISTORS

Back 16

the resistor limits the current in the circuit (when the LED conducts)
otherwise it could overheat/burn out/be damaged/AW

Front 17

WAVELENGTH
FREQUENCY
SPEED

Back 17

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

Front 18

EQUATION V=F(WVLEGT)

Back 18

in 1 second f waves are produced each of one wavelength λ
distance travelled by first wave in one second is f λ = v

Front 19

INFRARED RADIATION

Back 19

infra red is part of the e-m spectrum
lower f or longer λ than the visible region/light or suitable value or range
of λ

Front 20

INTERFERENCE

Back 20

when (two) waves meet/combine/interact/superpose, etc. (at a point)
there is a change in overall intensity/displacement

Front 21

COHERENCE

Back 21

constant phase difference/relationship (between the waves)

Front 22

PATH DIFF VS PHASE DIFFERENCE

Back 22

path difference of nλ for constructive interference
producing either maximum amplitude/intensity or a maximum
path difference of (2n + 1)λ/2 for destructive interference
producing either minimum amplitude/intensity or a minimum

Front 23

ENERGY LEVELS AND EXPLAIN EMISSION OF PHOTONS FROM ATOMS

Back 23

energy levels explanation: 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

Front 24

DIFFRACTION

Back 24

paths spread out after passing through a gap or around an obstacle

Front 25

ELECTRONS PRODUCING DIFFRACTION

Back 25

wavelength of electrons
must be comparable/of the order of magnitude of the atomic spacing

Front 26

BROGLIE

Back 26

λ = h/mv

Front 27

ELECTRON GUN CONNECTED TO NEGATIVE TERMINAL

Back 27

electrons should be repelled by cathode and/or attracted by anode or
they will be attracted back to the cathode/slowed down if cathode positive

Front 28

POTENTIAL DIFFERENCE

Back 28

energy transfer per unit charge
from electrical to other forms

Front 29

WORK FUNCTION

Back 29

the minimum energy (required) to release an electron (from the
surface of the metal)

Front 30

MAALUS LAW

Back 30

I = I
0 cos
2
θ
where I
0 is the maximum intensity (of the polarised beam)
B1
B1 allow incident/original/initial for maximum
when θ is zero maximum intensity transmitted/ image bright
when θ is 90
o
minimum/zero intensity transmitted/image
dim/vanished

Front 31

PROGRESSIVE WAVES

Back 31

is a transfer of energy
as a result of oscillations (of the source/medium/particles
through which energy is travelling)

Front 32

TRANSVERSE VS LONGITUDINAL

Back 32

displacement/oscillation (of particles) is
normal/perpendicular to direction of energy transfer in
transverse wave
displacement/oscillation (of particles) is parallel to direction
of energy transfer in longitudinal wave

Front 33

DIFRACTION

Back 33

wavefronts/paths spread out after passing through a gap
or around an obstacle/AW

Front 34

LOUDER INTENSE

Back 34

waves superpose/interfere at points along PQ
(constructively and destructively)
path difference from sources of nλ for maximum/loud
sound/intensity
path difference of (2n + 1)λ/2 for minimum/quiet
sound/intensity

Front 35

STATIONARY WAVES

Back 35

energy is trapped in pockets/ where the shape or energy
does not move along/energy is stored/AW
there are nodes/positions of zero amplitude/motion
there are positions where there is max.
amplitude/antinodes
different/adjacent points have different amplitudes/AW
all points between nodes in phase/all points in adjacent
/2’s in anti-phase/AW