Dual Nature Of Light Question 120
Question: In the following arrangement y = 1.0 mm, d= 0.24 mm and D = 1.2 m. The work function of the material of the emitter is 2.2 eV. The stopping potential V needed to stop the photo current will be
Options:
A) 0.9 V
B) 0.5 V
C) 0.4 V
D) 0.1 V
Show Answer
Answer:
Correct Answer: A
Solution:
As we know in Young’s double slit experiment fringe width = separation between two consecutive fringe or dark fringes $ =\beta =\frac{\lambda D}{d} $ Here $ \beta =2y $
Þ $ 2y=\frac{\lambda D}{d} $
Þ $ \lambda =\frac{2yd}{D} $
Þ $ \lambda =\frac{2\times 1\times {{10}^{-3}}\times 0.24\times {{10}^{-3}}}{1.2}=4\times {{10}^{-7}}m=4000,{\AA} $ Energy of light incident on photo plate $ E,(eV)=\frac{12375}{4000}=3.1,eV $ According to Eienstein photoelectric equation E = W0 + eV0
Þ $ V_{0}=\frac{(E-W_{0})}{e}=\frac{(3+2.2)}{e}eV,\approx 0.9,V $
BETA
