Dual Nature of Radiation and Matter NEET PYQs (1989–2026)

Solved Dual Nature of Radiation and Matter PYQs

3 recent questions with answers. The full set of 108 is free to practise.

1. NEET 2026EasyWave Nature of Matter – de Broglie
   Q1

   A photon and an electron, each of $20eV$ energy, move in free space. The ratio of linear momentum of electron $p_e$ to that of photon $p_{Ph}$ $\frac{p_e}{p_{Ph}}$ is: [Take speed of light $=3\times 10^8{ms}^{-1}$, charge of electron $=-1.6\times 10^{-19}C$ and mass of electron $=9\times 10^{-31}kg$]

   • A$\frac{2}{450}$
   • B$\frac{1}{250}$
   • C225
   • D275

   Show answer & solution

   Correct answer: (C)

   For photon:
   
   $$p_{Ph}=\frac{E}{c}=\frac{20\times 1.6\times 10^{-19}}{3\times 10^8}=\frac{32\times 10^{-19}}{3\times 10^8}=1.0667\times 10^{-26}$$
   
   kg m/s.
   
   For electron: $E=\frac{p^2}{2m}$
   
   $$\Rightarrow p_e=\sqrt{2mE}=\sqrt{2\times 9\times 10^{-31}\times 20\times 1.6\times 10^{-19}}=\sqrt{5.76\times 10^{-48}}=2.4\times 10^{-24}$$
   
   kg m/s.
   
   $\frac{p_e}{p_{Ph}}=\frac{2.4\times 10^{-24}}{1.0667\times 10^{-26}}=225$.
2. NEET 2026HardThreshold Frequency, Stopping Potential, Work Function
   Q2

   A ray of light with wavelength $\lambda$ is incident on three different photoelectric cells namely 1, 2 and 3. The threshold wavelength of these photoelectric cells are ${\lambda }_1$, ${\lambda }_2$, and ${\lambda }_3$, respectively and the magnitude of stopping potentials of these cells are $V_1$, $V_2$ and $V_3$, respectively. The relation between $\lambda$ and threshold wavelengths are ${\lambda }_1<{\lambda }_2>\lambda$ and ${\lambda }_3>\lambda$. The correct option is:

   • A$V_1=0,V_2<V_3$
   • B$V_1=0,V_2>V_3$
   • C$V_1>V_2,V_3=0$
   • D$V_1<V_2,V_3=0$

   Show answer & solution

   Correct answer: (A)

   Photoelectric effect occurs only if $\lambda <{\lambda }_{threshold}$.
   
   For cell 1: ${\lambda }_1<\lambda$, so $\lambda >{\lambda }_1$, hence
   
   no photoemission, $V_1=0$.
   
   For cell 3: ${\lambda }_3>\lambda$, so $\lambda <{\lambda }_3$,
   
   photoemission occurs.
   
   For cell 2: ${\lambda }_2>\lambda$, photoemission occurs.
   
   Since ${\lambda }_2>{\lambda }_3$? Actually given
   
   ${\lambda }_1<{\lambda }_2>\lambda$ and ${\lambda }_3>\lambda$. We
   
   need to compare stopping potentials. Stopping potential
   
   $V\propto \left(1/{\lambda }_{threshold}-1/\lambda \right)$. Since
   
   ${\lambda }_2>{\lambda }_3$ (both > $\lambda$),
   
   $1/{\lambda }_2<1/{\lambda }_3$, so $V_2<V_3$. Thus
   
   $V_1=0,V_2<V_3$.
3. NEET 2025HardWave Nature of Matter – de Broglie Hypothesis
   Q3

   De-Broglie wavelength of an electron orbiting in the $n=2$ state of hydrogen atom is close to (Given Bohr radius $=0.052nm$ )

   • A1.67 nm
   • B2.67 nm
   • C0.067 nm
   • D0.67 nm

   Show answer & solution

   Correct answer: (D)

   The De-Broglie wavelength of an electron in the $n=2$ state of a hydrogen atom can be calculated as follows:
   Firstly, calculate the radius $r$ for the $n=2$ state using the Bohr radius formula:
   
   $$r=0.052n^2$$
   
   For $n=2$, the radius is:
   
   $$\begin{array}{cc}r& =0.052\times 4\\ & =0.208nm\end{array}$$
   
   We use the relationship $Mvr=\frac{nh}{2\pi }$, leading to the expression for the De-Broglie wavelength $\lambda$ :
   
   $$\lambda =\frac{h}{Mv}=\pi r$$
   
   Substituting the calculated $r$ value:
   
   $$\begin{array}{cc}\lambda & =\pi \times 0.208nm\\ & =3.14\times 0.208nm\\ & =0.65317nm\\ & \approx 0.67nm\end{array}$$
   
   Thus, the De-Broglie wavelength of the electron in the $n=2$ state is approximately 0.67 nm .

Topic-wise question count

Where NEET has asked from Dual Nature of Radiation and Matter, most frequent first.

• Photoelectric Effect40
• Wave Nature of Matter – de Broglie Hypothesis31
• Threshold Frequency, Stopping Potential and Work Function30
• Threshold Frequency, Stopping Potential, Work Function3
• Davisson–Germer Experiment3
• Wave Nature of Matter – de Broglie1

Year-wise Dual Nature of Radiation and Matter questions in NEET

Number of questions from this chapter in each year's paper(s).