The number of photons emitted per nanosecond by a deuterium lamp (400 nm) having a power of 1 microwatt (rounded off to the nearest integer) is \(\underline{\hspace{2cm}}\).
Given: \( h = 6.626 \times 10^{-34} \, \text{kg m}^2 \text{s}^{-1}, c = 3.0 \times 10^8 \, \text{m s}^{-1} \).
