(iii) A consequence of the Free Electron approach is that theelectron mass me effectively becomes a variable, the so-calledeffective mass, me * , which is governed by the curvature of the Ekvs. k function. Show that where the curvature of this function islarge the effective mass is small. [4 marks]
(iv) It is often found that some ‘useful’ semiconductors such assilicon or gallium arsenide have bands which show a high degree ofcurvature, whereas many insulators do not. Discuss how thisinfluences the properties of each type of material.
