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

Electrons orbit the nucleus in fixed energy levels

Answer

Electrons can be shared between atoms

Answer

Light always behaves as a wave

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

Both conserve kinetic energy

Answer

Inelastic collisions conserve kinetic energy

Answer

Elastic collisions occur only in gases

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 energy of photons

Answer

The speed of electrons in an orbit

Answer

The energy levels in a hydrogen atom

Question 4

What is Ohm's Law?

Accepted Answer

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

Answer

Power = voltage × current

Answer

Resistance = voltage + current

Answer

Current = resistance ÷ voltage

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

A wave that travels faster than sound

Answer

A wave with no frequency

Answer

A wave only found in solids

Question 6

What is the significance of the Hubble constant?

Accepted Answer

It relates the recession velocity of galaxies to their distance (v = H₀d), showing the universe is expanding

Answer

It measures the density of the universe

Answer

It describes the rate of nuclear decay

Answer

It measures the speed of light