Answer
$8.0 \times 10^{-24} J$.
Work Step by Step
Frequency equals speed/wavelength.
$$f = \frac{3 \times 10^{8} m/s}{2.5 \times 10^{-2} m} = 1.2 \times 10^{10} Hz$$
For photons, E = hf, where E is the energy, h is Planck's constant, and f is the photon's vibrational frequency.
$$ E = hf = (6.63 \times 10^{-34} J s)(1.2 \times 10^{10} Hz)$$
$$= 8.0 \times 10^{-24} J$$
