List of top Physics Questions on Dual nature of matter asked in CBSE CLASS XII

Choose the correct statement:

Two beams, A and B whose photon energies are $3.3 \, \text{eV$ and $11.3 \, \text{eV}$ respectively, illuminate a metallic surface (work function $2.3 \, \text{eV}$) successively. The ratio of maximum speed of electrons emitted due to beam A to that due to beam B is:}

Consider a neutron (mass $m$) of kinetic energy $E$ and a photon of the same energy. Let $\lambda_n$ and $\lambda_p$ be the de Broglie wavelength of the neutron and the wavelength of the photon, respectively. Obtain an expression for $\frac{\lambda_n{\lambda_p}$.}

The variation of the stopping potential \( V_0 \) with the frequency \( \nu \) of the incident radiation for four metals A, B, C, and D is shown in the figure. For the same frequency of incident radiation producing photo-electrons in all metals, the kinetic energy of photo-electrons will be maximum for which metal?

The minimum intensity of white light that our eyes can perceive is about \(0.1 \, nWm}^{-2}\). Calculate the number of photons of this light entering our pupil (area \(0.4 \, cm}^2\)) per second.
(Take average wavelength of white light \(= 500 \, nm}\) and Planck’s constant \(= 6.6 \times 10^{-34} \, Js}\).) % Correct answer Correct Answer: To find the number of photons, we first calculate the energy per photon using the equation for photon energy: \[ E = \frac{hc}{\lambda} \] where \( h = 6.6 \times 10^{-34} \, Js} \) (Planck's constant), \( c = 3 \times 10^8 \, m/s} \) (speed of light), and \( \lambda = 500 \, nm} = 500 \times 10^{-9} \, m} \).

Assertion (A): Photoelectric effect demonstrates the particle nature of light.
Reason (R): Photoelectric current is proportional to frequency of incident radiation.

Which one of the following is the correct graph between the maximum kinetic energy (\( K_m \)) of the emitted photoelectrons and the frequency of incident radiation (\( \nu \)) for a given photosensitive surface?
\includegraphics[width=0.5\linewidth]{10o.png}

de Broglie wavelength \( \lambda \) as a function of \( \frac{1}{\sqrt{K}} \), for two particles of masses \( m_1 \) and \( m_2 \), is shown in the figure. Here, \( K \) is the energy of the moving particles. (a) What does the slope of a line represent? 
(b) Which of the two particles is heavier? 
(c) Is this graph also valid for a photon? Justify your answer in each case.

 

Assertion (A): Photoelectric current increases with an increase in intensity of incident radiation, for a given frequency of incident radiation and the accelerating potential.
Reason (R): Increase in the intensity of incident radiation results in an increase in the number of photoelectrons emitted per second and hence an increase in the photocurrent.

Assertion (A): In photoelectric effect, the kinetic energy of the emitted photoelectrons increases with increase in the intensity of the incident light.
Reason (R): Photoelectric current depends on the wavelength of the incident light.

A proton and an \( \alpha \)-particle are accelerated through different potentials \( V_1 \) and \( V_2 \) respectively so that they have the same de Broglie wavelengths. Find \( \frac{V_1}{V_2} \).

The quantum nature of light explains the observations on the photoelectric effect as: