Fireflies emit flashes of light to communicate, directly converting chemical ene

Question

Fireflies emit flashes of light to communicate, directly converting chemical energy into the energy of visible-light photons. A firefly emits a 0.17 s long pulse of light with an average wavelength of 610 nm. During the flash, the emitted power is 40 micro watts.


What is the energy of one light photon having the average wavelength?
Where E = ?eV
Express your answer using two significant figures.

Assume that all photons have the average wavelength. How many photons does the firefly emit during each flash?
N= ?
Express your answer using two significant figures.

Explanation / Answer

Energy = hc/wavelength h= plancks consatnt = 4.135667516(91)×10-15 e.v.s c= light velocity = 3 * 10 ^8 m/s wavelength = 610 * 10 ^-9 m energy = 4.135667516(91)×10-15* 3 * 10 ^8 /610 * 10 ^-9 = 0.67786 e.v= 0.68 ev for one photon energy of N photons = N* 0.67786 e.v emitted power = energy of N photons/ time = 40 * 10 ^ -6 j/s 1 .ev.= 1.602×10-19joule N* 0.67786 * 1.602×10-19/0.17(s)= 40 * 10 ^-6 N=6.2619* 10 ^13 photons= 6.26 * 10 ^ 13

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