Einsteins Photoelectric Equation - UNSOLVED PRACTICE SET

Q7. State Einstein's photoelectric equation and explain each term.

Q8. How does Einstein's explanation of the photoelectric effect differ from the classical wave theory explanation?

Q9. Draw a graph of stopping potential versus frequency of incident light for a given photosensitive material. What information can be obtained from the slope and intercept of this graph?

Q10. Why does Einstein's photoelectric equation successfully explain the instantaneous nature of photoelectric emission?

Q11. Explain how Einstein's concept of photons accounts for the fact that the maximum kinetic energy of photoelectrons depends on frequency but not on intensity.

Q12. What would be the effect on the photoelectric emission if the intensity of incident light is doubled without changing its frequency

Q13. State and explain Einstein's photoelectric equation. Show how it successfully explains all the observations of the photoelectric effect that could not be explained by wave theory.

Q14. Derive Einstein's photoelectric equation from the principle of conservation of energy. Explain how this equation leads to the concept of threshold frequency.

Q15. Explain how the graph of maximum kinetic energy of photoelectrons versus frequency of incident light is used to determine:

(a) Planck's constant

(b) Threshold frequency

(c) Work function

Draw the graph and label all important features.

Q16. Light of wavelength 300 nm falls on a metal surface having a work function of 2.5 eV.

(a) Calculate the energy of each incident photon in eV.

(b) Using Einstein's photoelectric equation, calculate the maximum kinetic energy of the emitted photoelectrons.

(c) Calculate the stopping potential.

(d) If the intensity of the incident light is doubled, what changes occur in the stopping potential and the photoelectric current?

Q17. The graph of stopping potential versus frequency for a photosensitive surface is a straight line with slope 4.14 × 10⁻¹⁵ V·s and x-intercept at 5 × 10¹⁴ Hz.

(a) Calculate Planck's constant from the slope.

(b) Calculate the threshold frequency.

(c) Calculate the work function of the material in eV.

(d) Calculate the stopping potential when light of frequency 8 × 10¹⁴ Hz is incident on the surface.

Q18. In your school's physics lab, a student studies the photoelectric effect using a sodium photocell and obtains the following data:

Table

Frequency (×10¹⁴ Hz) Stopping Potential (V)

6.0 0.24

7.0 0.65

8.0 1.07

9.0 1.48

10.0 1.89

(a) Plot a graph of stopping potential versus frequency.

(b) From the graph, determine the threshold frequency.

(c) Calculate the slope of the graph and hence determine Planck's constant.

(d) Calculate the work function of sodium.

(e) A classmate suggests that if they use a more intense light source, the graph will shift upward. Explain why this is incorrect and what actually happens when intensity is increased.