The answer to the question, how many photons per second are emitted from the laser is d. 1.84 × 10¹⁵ photons/sec
Since the red laser pointer emits light of wavelength 488 nm, we need to find the energy of each photon from
E = hc/λ where h = Planck's constant = 6.63 × 10⁻³⁴ Js, c = speed of light = 3 × 10⁸ m/s and λ = wavelength of light = 488 nm = 488 × 10⁻⁹ m
Substituting the values of the variables into the equation, we have
E = hc/λ
E = 6.63 × 10⁻³⁴ Js × 3 × 10⁸ m/s ÷ 488 × 10⁻⁹ m
E = 19.89 × 10⁻²⁶ Jm ÷ 488 × 10⁻⁹ m
E = 0.04076 × 10⁻¹⁷ J per photon
E = 4.076 × 10⁻¹⁹ J per photon
Since the laser emits 7.5 × 10⁻⁴ J per second, the number of photons emitted from the laser per second = energy per second/energy per photon
= 7.5 × 10⁻⁴ J per second ÷ 4.076 × 10⁻¹⁹ J per photon
= 1.84 × 10¹⁵ photons/sec
The answer to the question, how many photons per second are emitted from the laser is d. 1.84 × 10¹⁵ photons/sec
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