The correct option is A 30 W
Energy E of photons of frequency ν is given by E=hν. If the lamp emits n photons per second, then the power of the lamp is P=nhν.
Now, ν=cλ
Therefore, P=nhcλ
=1020×6.6×10−34×3×108660×10−9=30 W
Hence, the correct choice is (a).