Calculate the velocity of electrons ejected from a surface of sodium metal (work function=2.28 eV) when it is irradiated with a light wave of 2x10¹⁵Hz. [4 Marks].

Describe the advantages of wavelength dispersive spectroscopy over energy dispersive spectroscopy in studying the distribution of chemical elements within the microstructure of materials containing multiple chemical elements. [3 Marks].

Consider the two 1D lattice systems of monoatomic and diatomic chains shown in fig. 1, and 2, respectively. Sketch the corresponding dispersion curves assuming that the atoms in both lattices can move only along the chain direction. [4 marks].