1. an energy gap of a semiconductor has its fermi level just above valence band of 0.2ev and the energy gap is 1.5ev
a) deduce the type of majority carriers
b) calculate the probability of a hole occupying a state at the top of valence band.

2. effective number of states per unit volume in valence and conduction bands is
n=2(2πm*kbt/h^2)^2/3
where m*=effective mass
m*e=0.02me, m*h=0.05me
i) calculate density of state in valence at room temperature
ii) deduce the concentration of holes in valence at room temperature
note* b and e are subscripts

layer a is the exosphere and layer b is the thermosphere.   is the answer i think but i hope this .

c.the charges if the proton and electron and gravity

answer: option c.

explanation:

the order for strong to weak forces such as

strong nuclear force → electromegnetic force → weak nuclear force → gravitational force

the fundamental forces are those forces that act between to objects or element to make interactions. there are four types of fundamental forces such as strong and weak nuclear forces (due to protons and electrons), electromagnetic force (due to the motion of electrons) and gravitational force (due to orbital movement of the planet). if these forces are arranged on the basis of their maximum strength then the order is

strong nuclear force → electromegnetic force → weak nuclear force → gravitational force