Verify that the hydrogen $1s \to 2p$ transition rate matches the known value $A = 6.27 \times 10^8\,\text{s}^{-1}$. - Confirm that $1s \to 2s$ gives $|\vec{d}_{fi}| = 0$ (E1 forbidden). - Check that the ratio $A/B$ agrees with Einstein's formula. - Compare perturbative transition probability with ex