Using the experimental apparatus shown in figure 2, when ultraviolet light with

Question

Using the experimental apparatus shown in figure 2, when ultraviolet light with a wavelength of 200 nm shines on plate 1 electrons are emitted, crossing the gap to plate 2 and causing a current to flow through the wire connecting the two plates. The battery voltage is gradually increased until the current in the ammeter drops to zero, at which point the battery voltage is 1.10 V. a) What is the energy of the photons in the beam of light? b) What is the work function of the metal? C)What is the maximum kinetic energy of the emitted electrons? d) If we turn the battery off, what is the longest wavelength that would cause electrons to be emitted for this particular metal?

Explanation / Answer

lamda = 200 nm , stopping potentail Vo =1.1 V

(a) E = hc/lamda

E(eV) =1243/lamda(nm)

E = 1243/200 = 6.215 eV

(b) from photo electric effect equaiton

E = W + eVo

6.215 = W +1.1

W = 5.115 eV

(C) Kmax = eVo

Kmax = 1.1 eV

(d) W = hc/lamdao

5.115 = 1243/lamdao

lamdao =243 nm

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