*Simulator***Previous Years AIEEE/JEE Mains Questions**

Q. The surface of a metal is illuminated with the light of 400 nm. The kinetic energy of the ejected photoelectrons was found to be 1.68 eV. The work function of the metal is : (hc = 1240 eV-nm)
(1) 1.51 eV (2) 1.68 eV (3) 3.09 eV (4) 1.41 eV

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**Sol.**(4) $\mathrm{E}_{\mathrm{k}}=\frac{\mathrm{hc}}{\lambda}-\phi_{0} \Rightarrow 1.68=\frac{12400}{4000}-\phi_{0}$ By solving it $\phi_{0}=1.42 \mathrm{eV}$

Q.

**Statement-1 :**When ultraviolet light is incident on a photocell, its stopping potential is V0 and the maximum kinetic energy of the photoelectrons is $\mathrm{K}_{\mathrm{max}}$. When the ultraviolet light is replaced by X-rays, both $\mathrm{V}_{0}$ and $\mathrm{K}_{\mathrm{max}}$ increase.**Statement-2 :**Photoelectrons are emitted with speeds ranging from zero to a maximum value because of the range of frequencies present in the incident light (1) Statement–1 is true, Statement–2 is false (2) Statement–1 is true, Statement–2 is true; Statement–2 is the correct explanation of Statement– 1 (3) Statement–1 is true, Statement–2 is true; Statement–2 is not the correct explanation of Statement– 1 (4) Statement–1 is false, Statement–2 is true**[AIEEE – 2010]****Download eSaral App for Video Lectures, Complete Revision, Study Material and much more...**

**Sol.**(1) Speed of emitted electrons is independent of frequency of incident light.

Q. This question has Statememtn-1 and Statement-2. Of the four choices given after the statements, choose the one that best describes the two statements.

**Statement–1 :**A metallic surface is irradiated by a monochromatic light of frequency $\mathrm{v}>\mathrm{v}_{0}$ (the threshold frequency). The maximum kinetic energy and the stopping potential are $\mathrm{K}_{\max }$ and $\mathrm{V}_{0}$ respectively. If the frequency incident on the surface is doubled, both the $\mathrm{K}_{\max }$ and $\mathrm{V}_{0}$ are also boubled.**Statement-2 :**The maximum kinetic energy and the stopping potential of photoelectrons emitted from a surface are linearly dependent on the frequency of incident light. (1) Statement–1 is true, Statement–2 is true, Statement–2 is not the correct explanationof Statement– 1 (2) Statement–1 is false, Statement–2 is true (3) Statement–1 is true, Statement–2 is false (4) Statement–1 is true, Statement–2 is true, Statement–2 is the correct explanation of Statement– 1**[AIEEE-2011]**
Q. The anode voltage of photocell is kept fixed. The wavelength $\lambda$ of the light falling on the cathode is gradually changed. The plate current I of the photocell varies as follows

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**Sol.**(4) For constant intensity as wavelength decreases energy of photons increases and number of photons decreases. So it may seem that current should decrease. But the probability that a photon will be successful in emitting an electron will also increase. So as wavelength decreases current increases

Q. Radiation of wavelength $\lambda$, is incident on a photocell. The fastest emitted electron has speed v. If the wavelength of changed to $\frac{3 \lambda}{4}$, the speed of the fastest emitted electron will be :-

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**Sol.**(2) $\mathrm{E}=(\mathrm{KE})_{\max }+\mathrm{f}$ $\left[\frac{\mathrm{hc}}{\lambda}=(\mathrm{KE})_{\max }+\phi\right] \ldots .$ (1) \frac{4}{3} \frac{\mathrm{hc}}{\lambda}=\left(\frac{4}{3} \mathrm{KE}_{\max }+\frac{\phi}{3}\right)+\phi

Statement type question are tougher than numerical type question

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Nice start to encourage jee aspirants with previous year questions

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