The Hydrogen  Atom is described by the Bohr’s model.  You are required to calculate the wavelength of light that will be emitted (or absorbed) by the Hydrogen  Atom, when an electron goes from the 4th energy level (4th orbit)      to      the 2nd energy level (2nd orbit).  From this formula sheet, which formulas and in which order will you have to apply to calculate the wavelength ?  (An equation repeated twice in the list of options means that the same equation, with some modifications, is applied twice).  (1)

At some particular temperature, in the unit volume of an intrinsic semiconductor, the number of the broken covalent bonds is equal to 0 (Zero).    In this particular semiconductor, at this particular temperature, what can you say about the mobile carrier concentration? (build the matching pairs).

What is the meaning of a lattice constant a ?

What do we mean when we use the following notation (001), (011), (101), etc ?

Which of the following are the units of density (which was used in HW1)? Encircle All that apply. 

Before the Bohr’s model was introduced, it was believed that certain values are continuous (not discrete). Instead, the Bohr’s model suggested that those  values are “quantized” (discrete). What are those values that are “quantized” according to the Bohr’s model.  (Select All that apply)

You have an intrinsic semiconductor. It operates at room temperature. It does NOT have donors or acceptors.  Its energy Band-gap is 1 eV. Assume that the width of the Valence Band is more than 5 eV.   In this particular (intrinsic) semiconductor, which values of the energy an electron cannot have ?  Select All the correct statements below. 

Which of the following determines a particular color of light (encircle ALL answers that apply)

Which of the following are the units of concentration (e.g., concentration of free carriers)? Encircle All that apply. 

Photoelectric effect is when electrons escape from a metal when it is illumination with a light. If the energy of a photon of light is larger than the metal work-function, can an electron escape from the metal? If yes, what will be its kinetic energy after escaping?