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Question

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The laser in a compact disc player uses light with a wavelength of 720 nm. Calculate the energy of this radiation in joules per photon.
_____ J/photon
Calculate the energy of this radiation in kilojoules per mole of photons
.______ kJ/mol

Answer 1

The energy of a single photon of a specified wavelength (lambda) is given as:
E = h * c / lambda
Where E is the energy of the photon, h is Planck’s constant, c is the speed of light in a vacuum, and lambda is the wavelength o the light.
h = 6.63 E-34 Js
c = 299,792,458 m/s, which can be estimated as 3 E8 m/s for simplicity's sake

We are given than lambda = 720 nm = 720 E-9 m = 7.20 E-7 meters

Plugging into the equation, we get
E = 2.76 E-19 Joules per photon


1 mole of anything is 6.022 E23 of those things.
1 mole of photons is 6.022 E23 photons.
So to find the energy contained in 1 mole of the above described photons, multiply the energy per photon by the number of photons in 1 mole.
E = 2.76 E-19 J/photon * 6.022 photons / mol
E = 166358 Joules per mol
E = 166 kJ/mol

Answer 2

no clue srry.