Question

(a) A helium lamp is used for an experiment to study the photoelectric effect. The visible part of the spectrum emitted from the lamp is split into its components using a glass prism, which reveals a yellow spectral line at 587nm and a blue spectral line at 447nm.

(i) Explain briefly the origin of the distinct lines of different colour.

(ii) Has blue or yellow light higher energy (per photon)? Justify your answer.

(iii) The refractive index of the glass prism is larger for blue light than for yellow. Will the direction of blue or yellow light change by a larger angle compared to the incident light? Justify your answer.

(iv) Has blue or yellow light higher velocity within the glass prism? Justify your answer.

(b) The yellow light and blue light from part (a) hit a piece of potassium with work function 2.29 eV.

(i) Calculate the energy of the emitted photoelectrons.

(ii) Electrons are fermions. State the difference between fermions and bosons in terms of their spin quantum number.

(iii) Briefly explain the meaning of the Pauli exclusion principle.

(iv) A helium ion with total charge −e has 3 electrons. Show that there are four different combinations of spin magnetic quantum number that these electrons can have. Justify your answer on the basis of the aufbau principle.

Answer 1