Answer
a. The letter is g.
b. $2.90\times 10^{-7}eV$.
Work Step by Step
a. The $j$ quantum number takes the values $l+\frac{1}{2}$ and $l-\frac{1}{2}$.
If j has the values 7/2=3.5 and 9/2=4.5, it must be that $l=4$. The letter that labels this value is g.
b. Equation 41.41 gives the energy of each energy level. Calculate the energy for n = 5, using j = 7/2 and then j = 9/2, and subtract the values.
The energy difference is $2.90\times10^{-7}eV$.
