Modern Physics Quiz

Modern Physics: ten practice questions on quantum, nuclear, and relativistic effects, with concepts and calculations. Every answer is explained.

Free, with no sign-up.

For High school students and adults reviewing the topic.

About 15 minutes. 10 questions.

How does it work?

Choose one answer or enter a number in the stated unit and rounding, then check it.
Your first submitted answer counts toward the score. There is no timer.
Keep full precision during calculations and round only the final answer as requested.

What will you get?

See your first-attempt score and an explanation for every answer.

Question 1A photon has wavelength λ = 500 nm. Use E = hc/λ and hc = 1240 eV·nm. Find its energy in eV, rounded to two decimal places.

Enter a number in eV.

Answers within 0.005 eV of the expected value are accepted.

Question 2Light delivers photons of energy 5.0 eV to a surface with work function 2.0 eV. Find the maximum emitted-electron kinetic energy in eV, to two decimal places.

Enter a number in eV.

Answers within 0.005 eV of the expected value are accepted.

Question 3The fastest emitted electrons have kinetic energy 2.5 eV. Use 1 eV of energy change per volt for one electron. Find the stopping-potential magnitude in V, to two decimal places.

Enter a number in V.

Answers within 0.005 V of the expected value are accepted.

Question 4A spacecraft moves with v/c = 0.60, where c is vacuum light speed. Calculate the Lorentz factor, a dimensionless ratio, rounded to two decimal places.

Enter a number.

Answers within 0.005 of the expected value are accepted.

Question 5A sample initially contains 80 g of a radioactive isotope. Find the expected mass of that isotope remaining after 4 whole half-lives, in g to two decimal places.

Enter a number in g.

Answers within 0.005 g of the expected value are accepted.

Question 6An atom emits a photon when moving between allowed energy states. What sets the photon’s energy?

The average of the energies of the states involvedThe time interval between preparing the atom and detecting lightThe energy difference between the atom’s initial and final statesThe atom’s total energy before the photon was emitted

Question 7Electrons form an interference pattern while arriving as individual detector impacts. Which interpretation fits?

One quantum model describes interference and localized detectionEach electron switches between a classical bead and waveThe localized impacts make the interference an instrument errorThe detector creates interference by observing the electrons

Question 8Moving observers disagree about elapsed time. What does relativity require?

Each observer’s clock defines a different set of physical lawsTheir measurements obey precise transformation rulesThe observers can resolve the difference by correcting a faulty clockThe difference comes from light traveling at a different vacuum speed

Question 9What distinguishes a nuclear change from an ordinary electron-state transition?

It involves only a rearrangement of an atom’s outer electron statesIt requires the nucleus to contain electrons instead of nucleonsIt eliminates the need to conserve energy during the processIt changes the nucleus rather than only an electron’s bound state

Question 10What happens to energy when a particle and its antiparticle annihilate?

Energy cancels with the pair’s opposite electric chargesEnergy is stored in a charge left after the pair vanishesEnergy is conserved and carried by the particles producedEnergy becomes a separate conserved quantity called mass

Answer every question to see and share your score.

Read the topic guide