4. The human eye is a complex sensing device for visible light. The optic nerve needs a minimum of 2.0 x 10-17 J of energy to trigger a series of impulses that eventually reach the brain. (a) How many photons of red light (700.0 nm) are needed? (b) How many photons of blue light (475 nm) are needed? PLEASE POST WORKING OUT AND ANSWER THANKS I AM SO LOST

Question

4.  The human eye is a complex sensing device for visible light.  The optic nerve needs a minimum of 2.0 x 10-17 J of energy to trigger a series of impulses that eventually reach the brain.   (a)  How many photons of red light (700.0 nm) are needed? (b)  How many photons of blue light (475 nm) are needed? PLEASE POST WORKING OUT AND ANSWER THANKS I AM SO LOST

DrBob222 · Accepted Answer

I'll do my best for the work but you get the answers.
E = hc/wavelength
E = h*c/700E-9.
h is 6.626E-34 J.s
c is 3E8 m/s
This gives the energy of ONE photon of red light. Then
Efrom above x #photons = 2.0E-17
Solve for # photons.

Do the same for the blue light.