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+// chapter 9
+// example 9.2
+// Find the temperature at which number of electrons becomes 10 times
+// page 272
+clear;
+clc;
+//given
+Eg=0.67; // in eV (Energy band gap)
+k=1.38E-23; // in J/K (Boltzmann’s constant)
+T1=298; // in K (room temperature)
+e=1.6E-19; // in C (charge of electron)
+K=10; // ratio of number of electrons at different temperature
+// calculate
+Eg=Eg*e; // changing unit from eV to Joule
+// since ne=Ke*exp(-Eg/(2*k*T))
+// and ne/ne1=exp(-Eg/(2*k*T))/exp(-Eg/(2*k*T1)) and ne/ne1=K=10
+// therefore we have 10=exp(-Eg/(2*k*T))/exp(-Eg/(2*k*T1))
+// re-arranging the equation for T, we get T2=1/((1/T1)-((2*k*log(10))/Eg))
+T=1/((1/T1)-((2*k*log(10))/Eg)); // calculation of the temperature
+printf('\nThe temperature at which number of electrons in the conduction band of a semiconductor increases by a factor of 10 is \tT=%.f K',T);
+// Note: there s slight variation in the answer due to round off calculation