The photoelectric effectAQA A-Level Physics: Mind map

Exam questions on The photoelectric effect

1. A physics class directs light of different colours and intensities at a clean metal surface inside an evacuated tube. A sensitive ammeter detects any electrons emitted from the surface. The work function of the metal is 3.4 × 10⁻¹⁹ J.
   The intensity of light below the threshold frequency is increased greatly, but no electrons are emitted. Explain why.2 marks
2. In a vacuum photocell a reverse potential difference is applied across the tube and increased until the photocurrent just falls to zero. This potential difference is the stopping potential. For one frequency of light the fastest photoelectrons leave the metal surface with a kinetic energy of 2.4 × 10⁻¹⁹ J.
   Explain why the photoelectrons are emitted with a range of kinetic energies, up to a maximum value.2 marks
3. A clean metal surface with a work function of 3.6 × 10⁻¹⁹ J is illuminated with ultraviolet light of wavelength 320 nm.
   Calculate the maximum kinetic energy of the photoelectrons.3 marks