Monochromatic light (that is, light of a single wavelength) is to be absorbed by

Question

Monochromatic light (that is, light of a single wavelength) is to be absorbed by a sheet of photographic film and thus recorded on the film. Photon absorption will occur if the photon energy equals or exceeds 0.3 eV, the smallest amount of energy needed to dissociate an AgBr molecule in the film.

(a) What is the greatest wavelength of light that can be recorded by the film?
nm

(b) In what region of the electromagnetic spectrum is this wavelength located?

radiomicrowave     visibleinfraredultraviolet

Explanation / Answer

The work function of the film (W) = 0.3 eV = 4.81*10-20 J (1 eV = 1.602*10-19 J)

a) Let '' be the greatest wavelength of light that can be recorded by the film

W=(hc)/

=> = (hc)/W

=> =(6.6*10-34)(3*108)/(4.81*10-20)

=> = 4.12*10-6 m = 4120 nm (1nm = 10-9 m)

b) From the Electromagnetic spectrum, we can conclude that the wavelength is located in the ULTRAVIOLET region

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