1. The work function of a metal is the minimum energy needed to remove an electron from its surface. Which of the following correctly describes threshold frequency?

2. The photoelectric equation is hf = φ + E_k(max). If a photon of frequency 8.0 × 10¹⁴ Hz hits a metal with work function 2.1 eV, calculate the maximum kinetic energy of emitted photoelectrons. (h = 6.63 × 10⁻³⁴ J·s, 1 eV = 1.6 × 10⁻¹⁹ J)

3. Convert the following energy values:

4. In a photoelectric experiment, the stopping potential is 1.5 V. What is the maximum kinetic energy of the photoelectrons?

5. In a fluorescent tube, mercury atoms are excited when electrons collide with them. Explain the difference between excitation and ionisation:

6. An electron in a hydrogen atom drops from energy level E₂ = -1.51 eV to E₁ = -3.40 eV. Using hf = E₁ - E₂, calculate the frequency of the emitted photon.

7. Which of the following statements about line spectra are correct? (Select all that apply)

8. The de Broglie wavelength equation is λ = h/mv. Calculate the de Broglie wavelength of an electron moving at 2.0 × 10⁶ m/s. (mass of electron = 9.11 × 10⁻³¹ kg)

9. Electron diffraction experiments show that electrons behave like waves. What happens to the diffraction pattern when the momentum of electrons increases?

10. Explain how the photoelectric effect demonstrates the particle nature of light, whilst electron diffraction demonstrates the wave nature of matter:

Extension Challenge: Research how peer review helped validate quantum theory. Why was it important for Einstein's photoelectric effect explanation to be reviewed by other scientists?