Problem
An electron is trapped in an infinite well which is 250 pm wide and is in its ground state. How much energy must it absorb to jump up to the state with n=4?
Solution: standing waves => n(?/2)=L
E=p2/2m= h2/2m ?2 = n2h2/8mL2
E4-E1= (h2/8mL2)(42 -1) =15(6.63x10-34)2/[8(9.11x10-31)(250x10-12)2=90.3 eV