Answer:
3 photons
Explanation:
The energy of a photon (E) can be calculated by the expression:
E = h*c/λ
Where h is the Planck constant (6.63x10⁻³⁴ J.s), λ is the wavelength (550 nm = 5.50x10⁻⁷m), and c is the speed of the light (3.00x10⁸ m/s).
E= (6.63x10⁻³⁴ * 3.00x10⁸)/(5.50x10⁻⁷)
E = 3.62x10⁻¹⁹ J
Which is the energy of one photon. The human eye can respond to 10⁻¹⁸ J, so:
1 photon ------------------------ 3.62x10⁻¹⁹ J
x ----------------------- 10⁻¹⁸ J,
By a simple direct three rule
x = 2.76 ≅ 3 photons.
