Photoelectric EffectHard
Question
Photoelectric effect experiments are performed using three different metal plates p, q and r having work functions φp = 2.0 eV, φq = 2.5 eV and φr = 3.0 eV, respectively. A light beam containing wavelengths of 550 nm, 450 nm and 350 nm with equal intensities illuminates each of the plates. The correct I-V graph for the experiment is
Options
A.
B.
C.
D.
Solution
VB = (1/e)[(hc/λ) - φ]
Vp = (1/e)[(1240/550) - 2]eV = 0.2545 V
Vq = (1/e)[(1240/450) - 2.5]eV = 0.255 V
Vr = (1/e)[(1240/350) - 3]eV = 0.5428 V
If n is the number of photons in unit time then nhc/λ = I
⇒ ip : iq : ir = np : nq : nr = λp : λq : λr
Vp = (1/e)[(1240/550) - 2]eV = 0.2545 V
Vq = (1/e)[(1240/450) - 2.5]eV = 0.255 V
Vr = (1/e)[(1240/350) - 3]eV = 0.5428 V
If n is the number of photons in unit time then nhc/λ = I
⇒ ip : iq : ir = np : nq : nr = λp : λq : λr
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