Q: The graph between the stopping potential (V0) and (1/λ) is shown in figure, φ1 , φ2 and φ3 are work functions. Which of the following is correct
(a)φ1 :φ2 :φ3 = 1 : 2 : 4
(b) φ1 :φ2 :φ3 = 4 : 2 : 1
(c) tan θ is directly proportional to hc/e, where h is Planck’s constant and c is the speed of light
(d) ultraviolet light can be used to emit photoelectrons from metal 2 and meal 3 only.
Click to See Answer :
Sol: $ \displaystyle \frac{hc}{\lambda} = \phi + eV_0 $
$ \displaystyle V_0 = \frac{hc}{e \lambda}- \frac{\phi}{e} $
When λ = λ0 , K.E = 0
$ \displaystyle \frac{hc}{\lambda_0} = \phi $
$ \displaystyle \frac{\phi}{hc} = \frac{1}{\lambda_0} $
$ \displaystyle \frac{\phi_1}{hc} = 0.001 $
$ \displaystyle \frac{\phi_2}{hc} = 0.002 $
$ \displaystyle \frac{\phi_3}{hc} = 0.004 $
φ1 :φ2 :φ3 = 1 : 2 : 4