Question:
Work function of a metallic surface is 5.01 eV. When a light of wavelength 2000Å falls on the metallic surface, it emits photo electrons. The potential difference required to stop the fastest photo electron is? (in Volt)
Work function of a metallic surface is 5.01 eV. When a light of wavelength 2000Å falls on the metallic surface, it emits photo electrons. The potential difference required to stop the fastest photo electron is? (in Volt)
Show Hint
Use $E = \frac{12400}{\lambda\ (\text{in \AA})}$ to get photon energy instantly in eV. Subtract the work function, and the numerical value left is your stopping voltage!
Updated On: Jun 3, 2026
- 1.2
- 1.6
- 2.4
- 2.8
Show Solution
Verified By Collegedunia
The Correct Option is A
Solution and Explanation
Step 1: Concept
According to Einstein's photoelectric equation, the maximum kinetic energy of emitted photoelectrons is given by $K_{\max} = E - \phi$, where $E$ is the photon energy and $\phi$ is the work function. The stopping potential $V_{0}$ is related to $K_{\max}$ by $K_{\max} = eV_{0}$.
Step 2: Meaning
The energy of the incident photon in electron-volts can be calculated using the short formula $E = \frac{12400}{\lambda\ (\text{in \AA})}$.
Step 3: Analysis
Given $\lambda = 2000\text{ \AA}$ and $\phi = 5.01\text{ eV}$: $$E = \frac{12400}{2000} = 6.2\text{ eV}$$ Now, finding the maximum kinetic energy: $$K_{\max} = 6.2\text{ eV} - 5.01\text{ eV} = 1.19\text{ eV} \approx 1.2\text{ eV}$$ Since $K_{\max} = eV_{0}$, the stopping potential is $V_{0} = 1.2\text{ V}$.
Step 4: Conclusion
The stopping potential difference required is 1.2 V.
Final Answer: (A)
According to Einstein's photoelectric equation, the maximum kinetic energy of emitted photoelectrons is given by $K_{\max} = E - \phi$, where $E$ is the photon energy and $\phi$ is the work function. The stopping potential $V_{0}$ is related to $K_{\max}$ by $K_{\max} = eV_{0}$.
Step 2: Meaning
The energy of the incident photon in electron-volts can be calculated using the short formula $E = \frac{12400}{\lambda\ (\text{in \AA})}$.
Step 3: Analysis
Given $\lambda = 2000\text{ \AA}$ and $\phi = 5.01\text{ eV}$: $$E = \frac{12400}{2000} = 6.2\text{ eV}$$ Now, finding the maximum kinetic energy: $$K_{\max} = 6.2\text{ eV} - 5.01\text{ eV} = 1.19\text{ eV} \approx 1.2\text{ eV}$$ Since $K_{\max} = eV_{0}$, the stopping potential is $V_{0} = 1.2\text{ V}$.
Step 4: Conclusion
The stopping potential difference required is 1.2 V.
Final Answer: (A)
Was this answer helpful?
0
0
Top AP EAPCET Physics Questions
- A body is projected from the ground at an angle of $\tan^{-1} \left( \frac{8}{7}\right)$ with the horizontal. The ratio of the maximum height attained by it to its range is
- A lens forms real and virtual images of an object, when the object is at $u_{1}$ and $u_{2}$ distances respectively. If the size of the virtual image is double that of the real image, then the focal length of the lens is (take, the magnification of the real image as $m$ )
- Two spheres $P$ and $Q$, each of mass $200\, g$ are attached to a string of length one metre as shown in the figure. The string and the spheres are then whirled in a horizontal circle about $O$ at a constant angular speed. The ratio of the tension in the string between $P$ and $Q$ to that of between $P$ and $O$ is $(P$ is at mid-point of the line joining $O$ and $Q$ )
- The radii of the two columns in a U - tube are r1 and r2. When a liquid of density p (angle of contact is $ 0{}^\circ $ ) is filled in it, the level difference of the liquid in the two arms is h. The surface tension of the liquid is: (g = acceleration due to gravity)
- A rigid metallic sphere is spinning around its own axis in the absence of external torque. If the temperature is raised, its volume increases by $9 \%$. The change in its angular speed is
View More Questions
Top AP EAPCET Modern Physics Questions
- The ratio of the radii of the nuclei of mass numbers 27 and 64 is:
- The waves used for line of sight communication and satellite communication are:
- If a bullet of mass 2 g travels with velocity of 3 × 103 cm s-1, its wavelength (in m) is: (h = 6.6 × 10-34 Js)
- An electron of specific charge \( \frac{e}{m} \) enters an electric field, \( \vec{E} = -E_0 \hat{i} \) at a time \( t = 0 \) with an initial velocity \( \vec{v}_1 \). If \( \lambda_0 \) is its initial de Broglie wavelength, then its de Broglie wavelength at a time ‘t’ is
- If the angular momenta of electrons in two orbits of hydrogen atom are \( \frac{h}{\pi} \) and \( \frac{1.5h}{\pi} \), then the ratio of velocities of electrons in these two orbits is
(h – Planck’s constant)
View More Questions
Top AP EAPCET Questions
- A body is projected from the ground at an angle of $\tan^{-1} \left( \frac{8}{7}\right)$ with the horizontal. The ratio of the maximum height attained by it to its range is
- The four quantum numbers of the valence electron of potassium are :
- A lens forms real and virtual images of an object, when the object is at $u_{1}$ and $u_{2}$ distances respectively. If the size of the virtual image is double that of the real image, then the focal length of the lens is (take, the magnification of the real image as $m$ )
- Two spheres $P$ and $Q$, each of mass $200\, g$ are attached to a string of length one metre as shown in the figure. The string and the spheres are then whirled in a horizontal circle about $O$ at a constant angular speed. The ratio of the tension in the string between $P$ and $Q$ to that of between $P$ and $O$ is $(P$ is at mid-point of the line joining $O$ and $Q$ )
- The volume of $0.02\, M$ acidified permanganate solution required for complete reaction of $60\, mL$ of $0.01\, MI^{-}$ ion solution to form $I_2$ in $mL$ is
View More Questions