A-Level A-Level Physics

Question 1

What is the photoelectric effect and what does it prove?

Accepted Answer

When light of sufficient frequency hits a metal surface, electrons are emitted, proving light behaves as particles (photons)

Answer

The photoelectric effect: photons must have energy ≥ the work function to eject electrons. The emission depends on frequency, not intensity, proving light has particle-like properties (photons with E = hf). This challenged classical wave theory.

Question 2

What is the difference between elastic and inelastic collisions?

Accepted Answer

Elastic collisions conserve both momentum and kinetic energy; inelastic collisions conserve momentum but not kinetic energy (some KE is lost as heat or sound)

Answer

In elastic collisions, kinetic energy and momentum are both conserved (e.g., billiard balls). In inelastic collisions, momentum is conserved but kinetic energy is not — some is converted to heat, sound, or deformation.

Question 3

What does the de Broglie equation describe?

Accepted Answer

The wave-like behaviour of matter: λ = h/mv (wavelength of a particle)

Answer

The de Broglie equation λ = h/p = h/mv links the wavelength of a particle to its momentum. It demonstrates wave-particle duality: all matter has associated wavelength. At low mass/high speed (electrons), the wavelength is measurable.

Question 4

What is Ohm's Law?

Accepted Answer

Voltage = current × resistance (V = IR), for ohmic conductors at constant temperature

Answer

Ohm's Law states V = IR: the potential difference across a conductor is directly proportional to the current through it, provided temperature and other physical conditions remain constant. Materials that obey this are 'ohmic conductors'.

Question 5

What is a standing wave and what conditions are needed to form one?

Accepted Answer

A stationary pattern formed by superposition of two identical waves travelling in opposite directions, forming nodes and antinodes

Answer

Standing waves form when two waves of equal frequency and amplitude travel in opposite directions and superpose. They have fixed nodes (zero displacement) and antinodes (maximum displacement). They form in resonating systems like strings, pipes, and cavities.

A-Level Revision Practice Test

A-Level Revision Practice Test

A-Level A-Level Physics