Suppose 10⁻¹⁷ J of light energy is needed by the interior of the human eye to see an object. The number of photons of green light (λ = 550 nm) needed to see the object are
0.27
1.28
2.29
3.30
Explanation
E per photon = hc/λ = (6.625×10⁻³⁴ × 3×10⁸) / (550×10⁻⁹) = 3.614×10⁻¹⁹ J. n = 10⁻¹⁷ / 3.614×10⁻¹⁹ = 27.7 ≈ 28 photons