4 Electrons, Waves and Photons

Question 1

Power

Answer 1

The rate of work done. Amount of work done per unit time.

Question 2

1 Watt

Answer 2

The power of an engine which is converting 1J of energy in 1 second.

Question 3

Potential Difference

Answer 3

The energy per unit charge transferred from electrical potential energy to other forms.

Question 4

Current

Answer 4

The positive charge flowing per unit time.

Question 5

Resistance

Answer 5

The opposition to the flow of current. Given by the ratio of the voltage per unit amp. The voltage per unit current.

Question 6

Resistivity

Answer 6

A measure of a material’s ability to oppose the flow of an electric current given by RA/l, where R is the resistance of a uniform specimen of the material, having a length l and a cross-sectional are A.

Question 7

Mean Drift Velocity

Answer 7

The average distance travelled by an electron through a circuit, per unit time.

Question 8

EMF

Answer 8

The energy transferred from other forms to electrical energy, per unit charge, by charges passing through a supply.

Question 9

1 Coulumb

Answer 9

The charge that passes a point when a current of 1A flows for 1s.

Question 10

1 Volt

Answer 10

The potential difference across a 1 ohm resistor, which causes a current of 1A to flow.

Question 11

1 Ohm

Answer 11

The resistance of a resistor with potential difference of 1V across it and a current of 1A flowing through it,

Question 12

Ohm’s Law

Answer 12

For a metallic conductor at constant temperature, the current through it is directly proportional to the potential difference across its ends.

Question 13

1 Amp

Answer 13

The current flowing through a resistor of 1 ohm with a potential difference of 1V across it.

Question 14

Krichhoff’s 1st Law

Answer 14

The sum of the currents entering any point in a circuit will equal the sum of the currents leaving that same point.

Question 15

Krichhoff’s 2nd Law

Answer 15

The sum of the EMFs around a loop in a circuit is equal to the sum of the PDs in the same loop.

Question 16

Terminal Potential Difference

Answer 16

The potential difference between the actual contacts of a power supply. Given by the EMF of the supply minus the internal voltage drop.

Question 17

1 kW-hr

Answer 17

An amount of electrical energy equal to 3.6 million Joules of energy.

Question 18

Internal Resistance

Answer 18

Resistance within a battery.

Question 19

Wavelength

Answer 19

The distance of one full oscillation

Question 20

Frequency

Answer 20

The number of oscillations at a point per unit time

Question 21

Speed of a Wave

Answer 21

The distance travelled by a wave per unit time

Question 22

Reflection

Answer 22

The return of a beam of particles or waves when it encounters the boundary between two media

Question 23

Refraction

Answer 23

The change in direction of a wave as it crosses an interface between two materials where its speed changes.

Question 24

Diffraction

Answer 24

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

Question 25

Plane Polarised Waves

Answer 25

Transverse waves that oscillates only in one plane

Question 26

Principle of Superposition

Answer 26

When two or more waves meet at a point the resultant displacement is the sum of the displacement of the individual waves

Question 27

Interference

Answer 27

The formation of points of cancellation and reinforcement when two coherent waves pass through each other

Question 28

Coherence

Answer 28

Two sources are coherent when they emit waves with a constant phase difference

Question 29

Path Difference

Answer 29

The difference in distances travelled by two waves from coherent sources at a particular point

Question 30

Phase Difference

Answer 30

The fraction of a cycle between the oscillation of two points on the same wave, expressed in degrees or radians

Question 31

Constructive interference

Answer 31

When two waves reinforce to give increased amplitude

Question 32

Destructive interference

Answer 32

When two waves cancel to give reduced amplitude

Question 33

Intensity

Answer 33

The power transmitted normally through a surface per unit area

Question 34

Progressive wave

Answer 34

A transfer of energy as a result of oscillations

Question 35

Stationary wave

Answer 35

Energy is trapped in pocket containing nodes and antinodes

Question 36

Node

Answer 36

A point on a stationary wave with zero amplitude of oscillation

Question 37

Antinode

Answer 37

A point on a stationary wave with maximum amplitude of oscillation

Question 38

Fundamental mode of vibration

Answer 38

The mode of vibration with lowest frequency for a particular system

Question 39

Harmonic

Answer 39

An oscillation having a frequency that is a simple multiple of a fundamental frequency.

Question 40

Photon

Answer 40

A quantum of energy of electromagnetic radiation

Question 41

1 ElectronVolt

Answer 41

The energy gained by an electron travelling through a pd of 1V

Question 42

Work Function

Answer 42

The minimum energy required to release an electron from the metal surface

Question 43

Threshold Frequency

Answer 43

The minimum frequency of electromagnetic radiation that will eject electrons from the surface of a metal

Question 44

Line Spectra

Answer 44

A series of lines representing the wavelengths of the light emitted by an atom

Question 45

Absorption Spectra

Answer 45

A series of dark lines within a continuous spectrum