Physics OCR A A-Level (New Spec.)

Question 1

Brownian Motion

Answer 1

Random motion small visible particles (in a fluid) as a result of thermal bombardment by much smaller, invisible molecules.

Question 2

Ideal Gas Law

Answer 2

1. Large number particles
2. Rapidly, randomly
3. Collisions perfectly elastic
4. Negligible attractive forces
5. Time for collision negligible compared to time between
6. Particle = Negligible volume compared with volume of container

Question 3

Ideal Gas

Answer 3

Gas where internal energy only randomly distributed KE

Question 4

Boyle’s Law

Answer 4

pV= Constant under conditions of constant temperature for a fixed mass

Question 5

Charle’s Law
&
Pressure-Temperature Law

Answer 5

V/T = Constant

P/T= Constant

Question 6

Absolute Scale of Temperature

Answer 6

Scale measuring temperature independent of properties of any specific substance

Question 7

What three findings led to the standard model through Rutherford’s experiment?

Answer 7

Most a particles traveled through gold foil with little deflection (EMPTY SPACE)

a particles deflected away from nucleus, repulsive force necessary (NUCLEUS CHARGED)

Question 8

Why is radioactive decay described as a random and spontaneous event?

Answer 8

RANDOM: (1) Cannot predict when a particular nucleus will decay (2) Each nucleus within sample has the same chance of decay per unit time.

SPONTANEOUS: (1) Not affected by presence of other nuclei in the sample (2) External factors i.e. pressure

Question 9

Fundamental Particle

Answer 9

No internal structure & cannot be split into smaller particles

Question 10

Ionising Radiation

Answer 10

Radiation removes electrons from atom leaving it positively charged

Question 11

Radioactivity

Answer 11

Process by which unstable nuclei emit ionising radiation

Question 12

Activity

Answer 12

Rate at which nuclei decay (Bequerels)

Question 13

Annihalation

Answer 13

Complete destruction of particle and antiparticle that

Question 14

Binding Energy

Answer 14

Minimum energy required to completely separate a nucleus into its constituent protons and neutrons

Question 15

Thermal Neutrons

Answer 15

Neutron in fission reactor wuth mean KE similar to the Thermal energy of particles in the reactor core - slow neutrons

Question 16

Induced fission

Answer 16

Nuclear fission occuring when a nucleus becomes unstable on absorbing aother particle (i.e. neutron)

Question 17

Chain reaction

Answer 17

Reaction where neutrons from an earlier fission stage are responsible for further fission reactions leading to an exponential growth in the rate of reactions

Question 18

Moderator

Answer 18

Substance used to slow down the fast neutrons produced in fission reactions so they can propagate the fission reaction

Question 19

With what forces do Quarks & Leptons intra-act?

Answer 19

Quarks = Strong Nuclear force

Lepton= Weak Nuclear Force

Question 20

Why are gamma photons emitted?

Answer 20

When nucleus dropping to its ground state following the emission of an a or b particle.

Question 21

Measuring intensity of gamma radiation from source with a count rate may not be reliable, why?

Answer 21

• Gamma rays emitted in all directions so the detector only records those emitted in one direction.
• The efficiency of the detector is not 100%, the detector only records a fraction of the gamma rays that pass through it.
• The body of the sample itself may absorb some of the gamma rays inside of it.

Question 22

Describe what happens when a proton and antiproton meet, in terms if the photons (slow-moving)

Answer 22

Two Y-photons released with equal energy and travelling in opposite directions