Question

Topic: Spectroscopy

(1 point) Calculate the photons emitted per second from an Alexa488 dye pumped at 100 W/cm 2 .

Answer 1

given that

photon emitted per second = no. of photon emitted = (100 W/cm2 ) / energy of one photon.------------> (1)

So, if we calculate the energy of one photon, then we calculate a number of photons.

& we know that energy of one photon = hc / λ.

where h = plank's constant = 6.626 * 10^-34 Js, c= speed of light = 3 * 10^8m/s.

λ = emission wavelength of dye = 519 nm ( standard value).

So, the energy of one photon (E) emitted = (6.626 * 10^-34 * 3 * 10^8m/s) / 519 * 10^-9 m

E = 3.83 * 10^-15 J

put the value of E in equation (1)

w get,

no. of photon emitted = (100 * 10^^-4 W/m2) / 3.83 * 10^^-15 J

no. of photon emitted = 261.09 *10^¹⁰ s^-1.

if in question you assumed that energy loses during emission is zero then you should use wavelength = 488 nm, otherwise same as I have done.

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