What is the energy of a photon of infrared radiation with a frequency of 2.53 × 1012 Hz? Planck’s constant is6.63 × 10–34 J • s.

Use the photon energy formula E = hf, where h is Planck’s constant and f is frequency. Substituting gives E = (6.63 × 10⁻³⁴ J·s)(2.53 × 10¹² Hz) = 1.68 × 10⁻²¹ J; the seconds and hertz cancel. Therefore, the energy is 1.68 × 10⁻²¹ J, choice C.

AI-written and checked against the verified answer.