2.21 × 10^-18 Joules
We are given;
We are required to calculate the energy of the wave.
Thus, E = hc/λ
where, h is the plank's constant , 6.626 × 10^-34 J-s , c is the speed of light, 2.998 × 10^8 m/s, and λ is the wavelength.
Therefore;
E = (6.626 × 10^-34 J-s × 2.998 × 10^8 m/s) ÷ 9 × 10^-8 m
= 2.21 × 10^-18 Joules
Thus, the energy of the photon is 2.21 × 10^-18 Joules