A red laser pointer emits light at a wavelength of 488 nm.If the laser emits 7.5 $\times$ 10^-4 J of energy per second in the form of visible radiation,how many photons per second are emitted from the laser? A) 4.1 $\times$ 10^-19 photons/sec B) 5.4 $\times$ 10^-16 photons/sec C) 8.9 $\times$ 10¹⁴ photons/sec D) 1.8 $\times$ 10¹⁵ photons/sec E) 2.5 $\times$ 10¹⁸ photons/sec

Question

Quizplus · Accepted Answer

The energy of one photon is calculated using E = hc/λ. For λ = 488 nm, E ≈ 4.07 x 10^-19 J/photon. The number of photons per second is the total energy per second divided by the energy per photon: (7.5 x 10^-4 J/s) / (4.07 x 10^-19 J/photon) ≈ 1.8 x 10^15 photons/sec.

A Red Laser Pointer Emits Light at a Wavelength of 488