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Dual Nature of Radiation question

2025 · 24 Jan · Shift 2 · Q57
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  5. /2025 · 24 Jan · Shift 2 · Q57

Dual Nature of Radiation question

2025 · 24 Jan · Shift 2 · Q57

JEE MainPhysicsDual Nature of RadiationMCQ+4 / −1
In photoelectric effect, the stopping potential (V0)v/s\left(\mathrm{V}_0\right) \mathrm{v} / \mathrm{s}(V0​)v/s frequency (v)(v)(v) curve is plotted. ( h is the Planck's constant and ϕ0\phi_0ϕ0​ is work function of metal ) (A) V0v/sv\mathrm{V}_0 \mathrm{v} / \mathrm{s} vV0​v/sv is linear. (B) The slope of V0v/sv\mathrm{V}_0 \mathrm{v} / \mathrm{s} vV0​v/sv curve =ϕ0 h=\frac{\phi_0}{\mathrm{~h}}= hϕ0​​(C) h constant is related to the slope of V0v/sv\mathrm{V}_0 \mathrm{v} / \mathrm{s} vV0​v/sv line. (D) The value of electric charge of electron is not required to determine h using the V0v/sv\mathrm{V}_0 \mathrm{v} / \mathrm{s} vV0​v/sv curve. (E) The work function can be estimated without knowing the value of hhh. Choose the correct answer from the options given below :
  1. A
    (A), (C) and (E) only
  2. B
    (C) and (D) only
  3. C
    (A), (B) and (C) only
  4. D
    (D) and (E) only
View written solutionFree

Correct answer: A

  1. Use Einstein’s photoelectric equation

    For photoelectric effect, hν=ϕ0+Kmax⁡h\nu = \phi_0 + K_{\max}hν=ϕ0​+Kmax​

    and at stopping potential V0V_0V0​, Kmax⁡=eV0K_{\max} = eV_0Kmax​=eV0​

    So, eV0=hν−ϕ0eV_0 = h\nu - \phi_0eV0​=hν−ϕ0​

    Rearranging, V0=heν−ϕ0eV_0 = \frac{h}{e}\nu - \frac{\phi_0}{e}V0​=eh​ν−eϕ0​​

  2. Interpret the V0V_0V0​ vs frequency ν\nuν graph

    Comparing with straight line form y=mx+cy = mx + cy=mx+c, V0=(he)ν−ϕ0eV_0 = \left(\frac{h}{e}\right)\nu - \frac{\phi_0}{e}V0​=(eh​)ν−eϕ0​​

    Hence:

    • The graph of V0V_0V0​ vs ν\nuν is linear.
    • Slope =he= \dfrac{h}{e}=eh​.
    • Intercept on V0V_0V0​-axis =−ϕ0e= -\dfrac{\phi_0}{e}=−eϕ0​​.
    • Threshold frequency, ν0=ϕ0h\nu_0 = \frac{\phi_0}{h}ν0​=hϕ0​​
  3. Check each statement

    (A) V0V_0V0​ vs ν\nuν is linear.
    This is true.

    (B) Slope of V0V_0V0​ vs ν\nuν curve =ϕ0h= \dfrac{\phi_0}{h}=hϕ0​​.
    This is false because slope=he\text{slope} = \frac{h}{e}slope=eh​ not ϕ0h\dfrac{\phi_0}{h}hϕ0​​.

    (C) hhh constant is related to the slope of V0V_0V0​ vs ν\nuν line.
    This is true, since slope=he\text{slope} = \frac{h}{e}slope=eh​

    (D) The value of electric charge of electron is not required to determine hhh using the V0V_0V0​ vs ν\nuν curve.
    This is false because from slope, slope=he  ⟹  h=e×slope\text{slope} = \frac{h}{e} \implies h = e \times \text{slope}slope=eh​⟹h=e×slope so eee is required.

    (E) The work function can be estimated without knowing the value of hhh.
    This is true, because from the threshold frequency ν0\nu_0ν0​ obtained directly from the graph, V0=0⇒ν=ν0V_0=0 \Rightarrow \nu = \nu_0V0​=0⇒ν=ν0​ and if work function is expressed in electron-volt, ϕ0=eV=hν0\phi_0 = eV = h\nu_0ϕ0​=eV=hν0​ Also, from the intercept on the voltage axis, intercept=−ϕ0e\text{intercept} = -\frac{\phi_0}{e}intercept=−eϕ0​​ so numerically the work function in eV can be estimated from the graph without separately determining hhh.

  4. Correct set of statements

    True statements are: (A),(C),(E)\boxed{(A), (C), (E)}(A),(C),(E)​

    Therefore the correct option is: Option A\boxed{\text{Option A}}Option A​

  5. Comparison with stored answer

    Stored correct answer: A
    Derived answer: A
    Hence, they agree.

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