Paper 1 Definitions

Question 1

Moment?

Answer 1

Force times perpendicular distance from pivot.

Question 2

Couple?

Answer 2

A pair of of equal but opposite coplanar forces.

Question 3

Threshold frequency?

Answer 3

Minimum frequency required to eject photoelectrons.

Question 4

Work function?

Answer 4

Minimum energy required to remove an electron from the surface of a metal.

Question 5

Photoelectric effect?

Answer 5

Emission of electrons from a metals surface when electromagnetic radiation is incident upon it.

Question 6

Photoelectric emission?

Answer 6

Emission of electrons from a metal surface when light is directed at the surface.

Question 7

Excitation?

Answer 7

An electron has gained enough energy to move to a higher energy level.

Question 8

Ionisation?

Answer 8

When an electron gains enough energy to be completely removed from the atom from ground state.

Question 9

Free fall?

Answer 9

Motion of an object when experiencing an acceleration of g.

Question 10

Newton’s second law?

Answer 10

F = ma

Question 11

Amplitude?

Answer 11

Maximum displacement from the equilibrium position.

Question 12

Frequency?

Answer 12

Number of cycles per second passing a given point.

Question 13

Wavelength?

Answer 13

Length of one whole wave cycle.

Question 14

Phase?

Answer 14

Measurement of the position of a certain point along the wave cycle.

Question 15

Phase difference?

Answer 15

Amount one wave lags behind the other.

Question 16

Longitudinal wave?

Answer 16

Vibrations in same direction as energy transfer.

Question 17

Transverse wave?

Answer 17

Vibrations perpendicular to the direction of energy transfer.

Question 18

Elastic collisions?

Answer 18

KE conserved.

Question 19

Impulse?

Answer 19

Change in momentum.

Question 20

Stationary wave?

Answer 20

Superposition of two waves with the same frequency, moving in opposite directions.

Question 21

Coherent sources?

Answer 21

Same wavelength and frequency, and a fixed phase difference between them.

Question 22

Path difference?

Answer 22

Amount by which the path travelled by one wave is longer than the path travelled by the other wave.

Question 23

Constructive interference?

Answer 23

Path difference is a whole number of wavelengths.

Question 24

Destructive interference?

Answer 24

Path difference is half a wavelength or more half a wavelength value out of phase.

Question 25

Monochromatic light?

Answer 25

Same frequency and wavelength.

Question 26

Modal dispersion?

Answer 26

Light rays enter the fibre at different angles taking different paths, and so take different times to reach the end of the optical fibre.

Question 27

Material dispersion?

Answer 27

Light consists of different wavelengths that travel at different speeds. This causes some light wavelengths to reach the end of the fibre faster.

Question 28

1 joule?

Answer 28

Energy equal to the energy needed to raise a 1N weight through a height of 1 metre.

Question 29

Electric current?

Answer 29

Rate of flow of charge.

Question 30

Potential difference?

Answer 30

Work done per unit charge.

Question 31

One coulomb?

Answer 31

Amount of charge that passes in 1 second if the current is 1 amp.

Question 32

Ohmic conductor?

Answer 32

Current is directly proportional to the potential difference.

Question 33

Thermistor?

Answer 33

A resistor with a resistance that depends on temperature.

Question 34

Hooke's law?

Answer 34

Extension is proportional to applied force.

Question 35

Plastic deformation?

Answer 35

Material is permanently stretched.

Question 36

Young modulus?

Answer 36

A measure of the stiffness of a material.

Question 37

Power?

Answer 37

Rate of energy transfer.

Question 38

Internal resistance?

Answer 38

When chemical energy in a battery causes electrons to move and collide with one another.

Question 39

EMF?

Answer 39

Amount of electrical energy the battery produces for each coulomb of charge.

Question 40

Proton number?

Answer 40

Total number of protons in the nucleus.

Question 41

Nucleon number?

Answer 41

Total number of protons and neutrons.

Question 42

Isotopes?

Answer 42

Atoms with the same number of protons but different number of neutrons.

Question 43

Specific charge?

Answer 43

Charge to mass ratio.

Question 44

Nuclear force?

Answer 44

The force that overcomes the electrostatic repulsion between protons in the nucleus to keep the protons and neutrons together.

Question 45

Hypothesis?

Answer 45

An untested theory or idea.

Question 46

Photon?

Answer 46

Pack of electromagnetic waves.

Question 47

Scalar quantity?

Answer 47

Physical quantity which has magnitude only, no direction.

Question 48

Vector quantity?

Answer 48

Physical quantity which has magnitude and direction.

Question 49

Hadron?

Answer 49

Particles which feel the strong interaction.

Question 50

Uniform circular motion?

Answer 50

When an object rotates at a steady or constant rate.

Question 51

Centripetal force?

Answer 51

Resultant inward force towards the centre of the circle.

Question 52

SHM?

Answer 52

Acceleration of an object is directly proportional to its displacement from its equilibrium position in the opposite direction, and is directed towards the equilibrium.

Question 53

Free vibrations?

Answer 53

Involve no transfer of energy to or from the surrounding.

Question 54

Forced vibrations?

Answer 54

When there is no external driving forces.

Question 55

Natural frequency?

Answer 55

Frequency at which free oscillating systems oscillate at.

Question 56

Resonance?

Answer 56

When an oscillating system is forced to vibrate at a frequency close to its natural frequency. The amplitude of vibration increases rapidly to a maximum.