Four sources each send out electromagnetic waves with a power of 5.0 W: a radio transmitter at 100…

Step 1. The radio transmitter. $E = hf = 6.63 \times 10^{-34}\ \text{J s} \times 100 \times 10^{6}\ \text{Hz} = 6.63 \times 10^{-26}\ \text{J}$. So $N = \dfrac{5.0\ \text{W}}{6.63 \times 10^{-26}\ \text{J}} = 7.54 \times 10^{25}\ \text{s}^{-1}$.

Step 2. The green lamp. $hc = 6.63 \times 10^{-34} \times 3.00 \times 10^{8} = 1.989 \times 10^{-25}\ \text{J m}$. So $E = \dfrac{hc}{\lambda} = \dfrac{1.989 \times 10^{-25}\ \text{J m}}{550 \times 10^{-9}\ \text{m}} = 3.62 \times 10^{-19}\ \text{J}$. Then $N = 13.83 \times 10^{18}\ \text{s}^{-1}$.

Step 3. The X-ray source. $E = \dfrac{hc}{\lambda} = 1.99 \times 10^{-15}\ \text{J}$. So $N = 2.51 \times 10^{15}\ \text{s}^{-1}$.