HSC Physics — Module 7
Photoelectric Effect — Flashcards & Quiz
The photoelectric effect is a pivotal experiment in HSC Physics Module 7 that provided evidence for the particle nature of light. When photons hit a metal surface, electrons are ejected only if the photon energy (E = hf) exceeds the work function (φ). Einstein’s explanation — that light consists of quantised packets of energy — contradicted the classical wave model. You need to calculate kinetic energy of emitted electrons using Eₖ = hf - φ and explain why increasing intensity increases current but not maximum kinetic energy.
Sample Flashcards
Q1: Describe the photoelectric effect and why it was significant.
When light above a threshold frequency shines on a metal surface, electrons are ejected instantly. Increasing intensity increases the NUMBER of electrons but NOT their maximum KE. Only increasing frequency increases KE_max. This could NOT be explained by classical wave theory.
Sample Quiz Questions
Q1: Increasing the intensity of light below the threshold frequency will eventually eject electrons.
Answer: FALSE
No matter how intense the light, if its frequency is below the threshold, no electrons are ejected. Each photon lacks sufficient energy (hf < φ) and photon energies do not add up.
Q2: In the photoelectric effect, electrons are emitted instantaneously when light above the threshold frequency strikes the surface.
Answer: TRUE
This contradicted wave theory, which predicted a time delay. Einstein's photon model explains it — a single photon transfers all its energy to one electron instantly.
Last updated: March 2026 · 1 flashcards · 2 quiz questions