Question

In a photoelectric experiment the stopping potential for the incident light of wavelength $4000 \,\mathring{A} $ is 2 V. If the wavelength be changed to $3000 \mathring{A} $, the stopping potential will be

• A. 2 V
• B. zero
• C. less than 2 V
• D. more than 2 V

Answer 1

Answer: (D)

Photoelectric Effect,
$K E _{\max }= h v - W _{ o }$
The stopping potential,
$V _{ s } e = K E _{\max }$
$V _{ s } e = h v - W _{ o }$
$V _{ s } e =\frac{ h c }{\lambda}- W _{ o }$
From the above equation, as $\lambda$ decreases, $V _{ s }$ increases. Hence $V _{ s }> 2 V$