Question

The retina of a human eye can detect light when radiant energy incident on it is at least 4.00 × 10−17 J. For light of 535−nm wavelength, how many photons does this energy correspond to?

Answer 1

Answer:

1080 photons

Explanation:

ΔE = hc/λ => Energy per photon

h = 6.63 x 10⁻³⁴ j·s

c = 3 x 10⁸ m/s

λ= 535 nm = 5.35 x 10⁻⁷ m

ΔE/photon = (6.63 x 10⁻³⁴ j·s)(c = 3 x 10⁸ m/s)/(5.35 x 10⁻⁷ m) = 3.71 x 10⁻¹⁹ j/photon

For #photons in 4.00 x 10⁻⁷ j =  (4.00 x 10⁻⁷ j) / (3.71 x 10⁻¹⁹ j/photon) = 1076 photons ≅ 1080 photons (3 sig. figs.)