Dual Nature of Matter

JEE Main level, single correct, medium

156 of 200

Question 156 of 200

When radiation of wavelength λ\lambda is incident on a metallic surface, the stopping potential of ejected photoelectrons is 4.8V4.8V. If the same surface is illuminated by radiation of double the previous wavelength, then the stopping potential becomes 1.6V1.6V. The threshold wavelength of the metal is:

Show answer and solution

Answer: (B) 4λ4\lambda

VS=hv−ϕ{V}_{S}=hv-\phi
4.8=hcλ−ϕ...(i)4.8=\dfrac{hc}{\lambda }-\phi ...(i)
1.6=hc2λ−ϕ...(ii)1.6=\dfrac{hc}{2\lambda }-\phi ...(ii)
Using above equation (i)(i) −(ii)-(ii)
3.2=hcλ−hc2λ3.2=\dfrac{hc}{\lambda }-\dfrac{hc}{2\lambda }
3.2=hc2λ...(iii)3.2=\dfrac{hc}{2\lambda }...(iii)
[λ=hc6.4]\left[\lambda =\dfrac{hc}{6.4}\right]
Put in equation (ii)(ii)
ϕ=1.6\phi =1.6
hcλth=1.6\dfrac{hc}{{\lambda }_{th}}=1.6
λth=hc1.6{\lambda }_{th}=\dfrac{hc}{1.6}
=(hc6.4)×4=4λ=\left(\dfrac{hc}{6.4}\right)\times 4=4\lambda

JEE Main question paper PDF

Open a shift to read the full paper on this page, or download it.

JEE Main 2025 Apr 2 Shift 1 question paper

Open Download PDF

Opening paper…

Explain it as a whiteboard videoStep-by-step, in Hinglish or English. Your first video needs no login.Solved it on paper but got it wrong?Upload a photo of your working. Mistake Doctor marks the exact line that broke.
See it move: Photoelectric effect and matter waves simulationDrag the sliders and watch the numbers in this question change.Revise Modern Physics firstFormula sheet, solved examples and the traps students fall into.

More Physics practice

JEE Main Physics practice question on Dual Nature of Matter (Photoelectric Effect), with the answer and a step-by-step solution. Scan a question from your own book or paper to get a whiteboard video.