FRQ — Dual Nature of Radiation and Matter

Long answer·Standard multi-step (3/5)·Calculator allowed

Difficulty guide

The label describes the problem, not your ability.

1/5 - Foundational

Warm-up setup; checks one basic idea.

2/5 - Routine exam skill

Normal syllabus skill; usually one main rule or interpretation.

3/5 - Standard multi-step

Exam-style problem with multiple steps or a common trap.

4/5 - Hard exam skill

High-end exam problem; combines methods carefully.

5/5 - Challenge

Stretch problem beyond normal exam pressure.

Question

Light of wavelength

400\,\text{nm}

ejects electrons from a metal of work function

2.0\,\text{eV}

. Estimate the de Broglie wavelength of the fastest emitted electrons. Use

hc=1240\,\text{eV nm}

and

\lambda_e(\text{nm})=1.227/\sqrt{K(\text{eV})}

for electrons.

Total: 5 marks

(a) Find the maximum kinetic energy of the photoelectrons. (2 marks)

(b) Find the stopping potential. (1 mark)

Your response (optional — you can also work on paper)

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