Checkpoint 3 assesses L16, L20 in the published syllabus sequence.
Assessment is drawn only from this lesson’s repaired effective pool.
Assessment is drawn only from this lesson’s repaired effective pool.
This checkpoint assesses L16, L20 only. Lesson file IDs remain stable; displayed lesson numbers follow the module’s syllabus sequence.
1. The photoelectric effect is the ejection of electrons from a metal surface when...
2. The classical wave model of light FAILED to explain which observation about the photoelectric effect?
3. Einstein explained the photoelectric effect by proposing that light consists of...
4. The work function φ of a metal is...
5. The stopping potential V_s in a photoelectric experiment is the voltage needed to...
6. Light of frequency 1.0 × 10¹⁵ Hz strikes a metal with work function 2.0 eV. The maximum kinetic energy of emitted electrons is approximately...
7. If the intensity of light in a photoelectric experiment is doubled (frequency unchanged, above threshold), the maximum kinetic energy of emitted electrons...
8. The stopping potential for a photoelectric experiment increases when...
9. De Broglie's hypothesis states that all matter has a wavelength given by...
10. The Davisson-Germer experiment (1927) confirmed de Broglie's hypothesis by demonstrating...
11. The Heisenberg uncertainty principle states that the product of uncertainties in position and momentum satisfies...
12. Bohr's complementarity principle states that...
13. An electron moves at 2.0 × 10⁶ m/s. Its de Broglie wavelength is approximately...
14. Why do macroscopic objects (like a cricket ball) not exhibit observable wave behaviour?
15. In a single-electron double-slit experiment, each electron is detected as a point on the screen. Over many electrons, the pattern formed is...
SA1. State Einstein’s photoelectric equation, define its symbols and state the threshold condition. (4 marks)
SA2. A metal has work function 2.50 eV and is illuminated by 400 nm light. Calculate the photon energy and maximum electron kinetic energy. (4 marks)
SA3. Explain the different effects of increasing intensity and increasing frequency in a photoelectric experiment. (4 marks)
SA4. Describe the single-electron double-slit evidence and explain why reliable which-path information removes interference. (4 marks)
SA5. State de Broglie’s relation and its non-relativistic applicability condition. Explain why electron microscopes can outperform optical microscopes. (4 marks)
$K_{max}=hf-\phi$, where $h$ is Planck’s constant, $f$ is incident frequency and $\phi$ is the metal work function. Emission requires $hf\geq\phi$; at threshold $f_0=\phi/h$ and $K_{max}=0$.
$E=hc/\lambda\approx1240/400=3.10$ eV. Therefore $K_{max}=3.10-2.50=0.60$ eV, or $9.6\times10^{-20}$ J.
At fixed frequency above threshold and before collection saturation, greater intensity means more photons per second and therefore a larger photocurrent. Greater frequency raises each photon’s energy and therefore $K_{max}$ and stopping potential; intensity does not raise $K_{max}$.
Each electron is detected at one point, but many detections form an interference distribution when the paths remain indistinguishable. A which-path detector becomes entangled with the path alternatives. Distinguishable detector states remove their coherence, so the interference cross terms disappear; decoherence, not mere mechanical disturbance, is the general account.
$\lambda=h/p$ for any particle; for a non-relativistic particle $p=mv$, so $\lambda=h/(mv)$. Accelerated electrons can have wavelengths far shorter than visible light, reducing the diffraction-limited scale. At relativistic speeds the relativistic momentum must replace $mv$.