The human eye need's a minimum of 2.0x10^-17J of energy to trigger a serious of impulses that eventually reach the brain.
(a) How many photons of red light(700. nm) are needed?
(b) How many photons of blue light (475 nm)?
2006-10-17 16:00:18 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Physics
The energy of a photon is
E = f * h
f, frequency
h, planck constant.
f = c/Lambda
c, light speed
Lambda, wavelength
E = c*h/Lambda
for the minimum energy, Em, n photons will be required
Em = n * c * h / Lambda
n = Em * Lambda/ c / h
Plug the numbers and get n.,
2nd question, the same just change Lambda.
Good luck.
2006-10-17 16:09:21 · answer #1 · answered by Dr. J. 6 · 0⤊ 0⤋
The formula to give you the energy, in joules, of a photon is E= hc/l where h= Planck's constant 6.67x10^-34, c= speed of light 3x 10^8, l= wavelength in metres. So divide those wavelengths by 10^9 to convert nanometres to metres.
2006-10-17 16:07:49 · answer #2 · answered by zee_prime 6 · 0⤊ 0⤋
hoooooooooollllllllllllllyyyyyyyyyy................crrrrrrrraaaaaaaaaaapppppppppp.......now u dont learn THAT in 8th grade lol
2006-10-17 16:01:36 · answer #3 · answered by xenoith 2 · 0⤊ 0⤋