JEE Main 2025 January Physics: Dual Nature of Radiation & Matter – Previous Year Questions

The work functions of cesium (Cs) and lithium (Li) metals are 1.9 eV and 2.5 eV, respectively. If we incident a light of wavelength 550 nm on these two metal surfaces, then photo-electric effect is possible for the case of

A light source of wavelength $\lambda$ illuminates a metal surface and electrons are ejected with maximum kinetic energy of 2 eV. If the same surface is illuminated by a light source of wavelength $\frac{\lambda}{2}$, then the maximum kinetic energy of ejected electrons will be (The work function of metal is 1 eV)

In photoelectric effect, an em-wave is incident on a metal surface and electrons are ejected from the surface. If the work function of the metal is 2.14 eV and stopping potential is 2 V, what is the wavelength of the em-wave? (Given $hc = 1242$ eV nm where $h$ is the Planck's constant and $c$ is the speed of light in vacuum.)

In photoelectric effect, the stopping potential ($V_0$) v/s frequency ($\nu$) curve is plotted. ($h$ is the Planck's constant and $\phi_0$ is work function of metal)
(A) $V_0$ v/s $\nu$ is linear.
(B) The slope of $V_0$ v/s $\nu$ curve $= \dfrac{\phi_0}{h}$
(C) $h$ constant is related to the slope of $V_0$ v/s $\nu$ line.
(D) The value of electric charge of electron is not required to determine $h$ using the $V_0$ v/s $\nu$ curve.
(E) The work function can be estimated without knowing the value of $h$.
Choose the correct answer from the options given below :

The ratio of the power of a light source $S_1$ to that the light source $S_2$ is 2. $S_1$ is emitting $2\times10^{15}$ photons per second at 600 nm. If the wavelength of the source $S_2$ is 300 nm, then the number of photons per second emitted by $S_2$ is $\times10^{14}$.

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Emission of electrons in photoelectric effect can be suppressed by applying a sufficiently negative electron potential to the photoemissive substance.
Reason (R) : A negative electric potential, which stops the emission of electrons from the surface of a photoemissive substance, varies linearly with frequency of incident radiation.
In the light of the above statements, choose the most appropriate answer from the options given below :

In an experiment with photoelectric effect, the stopping potential,

A sub-atomic particle of mass $10^{-30}$ kg is moving with a velocity $2.21\times10^{6}$ m/s. Under the matter wave consideration, the particle will behave closely like . ($h = 6.63\times10^{-34}$ J.s)

An electron of mass ‘$m$’ with an initial velocity $\vec v = v_0\hat i$ ($v_0>0$) enters an electric field $\vec E = -E_0\hat k$. If the initial de Broglie wavelength is $\lambda_0$, the value after time $t$ would be

A proton of mass ‘$m_p$’ has same energy as that of a photon of wavelength ‘$\lambda$’. If the proton is moving at non-relativistic speed, then ratio of its de Broglie wavelength to the wavelength of photon is.

Which of the following phenomena can not be explained by wave theory of light ?

If $\lambda$ and $K$ are de Broglie wavelength and kinetic energy, respectively, of a particle with constant mass. The correct graphical representation for the particle will be