## Conceptual Physics (12th Edition)

$8.0 \times 10^{-24} J$.
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. $$E = hf = (6.63 \times 10^{-34} J s)(1.2 \times 10^{10} Hz)$$ $$= 8.0 \times 10^{-24} J$$