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Modern Physics — JEE Physics MCQs

Master Modern Physics for JEE Main with free physics MCQs. Each question includes a detailed solution and instant feedback — practice at easy, medium, and hard difficulty levels to build exam-ready confidence.

8 practice questions with instant feedback and solutions.

Easy•Modern Physics
The work function of a metal is 4.24.2 eV. The maximum wavelength of light that can eject photoelectrons from this metal is (Take hc=1240hc = 1240 eV·nm):
Hard•Modern Physics
The electrostatic energy of ZZ protons uniformly distributed throughout a spherical nucleus of radius RR is given by E=35Z(Z−1)e24πε0R E=\frac{3}{5} \frac{Z(Z-1) e^{2}}{4 \pi \varepsilon_{0} R} The measured masses of the neutron, 11H,715 N{ }_{1}^{1} \mathrm{H},{ }_{7}^{15} \mathrm{~N} and 815O{ }_{8}^{15} \mathrm{O} are 1.008665u,1.007825u1.008665 \mathrm{u}, 1.007825 \mathrm{u}, 15.000109u15.000109 \mathrm{u} and 15.003065u15.003065 \mathrm{u}, respectively. Given that the radii of both the 715 N{ }_{7}^{15} \mathrm{~N} and 815O{ }_{8}^{15} \mathrm{O} nuclei are same, 1u=931.5MeV/c21 \mathrm{u}=931.5 \mathrm{MeV} / c^{2} ( cc is the speed of light) and e2/(4πε0)=1.44MeVfme^{2} /\left(4 \pi \varepsilon_{0}\right)=1.44 \mathrm{MeV} \mathrm{fm}. Assuming that the difference between the binding energies of 715 N{ }_{7}^{15} \mathrm{~N} and 815O{ }_{8}^{15} \mathrm{O} is purely due to the electrostatic energy, the radius of either of the nuclei is (1fm=10−15 m)\left(1 \mathrm{fm}=10^{-15} \mathrm{~m}\right)
Hard•Modern Physics
A photoelectric material having work-function ϕ0\phi_{0} is illuminated with light of wavelength λ(λ<hcϕ0)\lambda\left(\lambda<\frac{h c}{\phi_{0}}\right). The fastest photoelectron has a de Broglie wavelength λd\lambda_{d}. A change in wavelength of the incident light by Δλ\Delta \lambda results in a change Δλd\Delta \lambda_{d} in λd\lambda_{d}. Then the ratio Δλd/Δλ\Delta \lambda_{d} / \Delta \lambda is proportional to [A]λd/λ[\mathrm{A}] \quad \lambda_{d} / \lambda [B]λd2/λ2[\mathrm{B}] \quad \lambda_{d}^{2} / \lambda^{2} [C]λd3/λ[\mathrm{C}] \lambda_{d}^{3} / \lambda [D]λd3/λ2[\mathrm{D}] \lambda_{d}^{3} / \lambda^{2}
Hard•Modern Physics
When light of a given wavelength is incident on a metallic surface, the minimum potential needed to stop the emitted photoelectrons is 6.0 V6.0 \mathrm{~V}. This potential drops to 0.6 V0.6 \mathrm{~V} if another source with wavelength four times that of the first one and intensity half of the first one is used. What are the wavelength of the first source and the work function of the metal, respectively? [Take hce=1.24×\frac{h c}{e}=1.24 \times 10−6 JmC−110^{-6} \mathrm{~J} \mathrm{mC}^{-1}.]
Medium•Modern Physics
A human body has a surface area of approximately 1 m21 \mathrm{~m}^{2}. The normal body temperature is 10 K10 \mathrm{~K} above the surrounding room temperature T0T_{0}. Take the room temperature to be T0=300 KT_{0}=300 \mathrm{~K}. For T0=300 KT_{0}=300 \mathrm{~K}, the value of σT04=460Wm−2\sigma T_{0}^{4}=460 \mathrm{Wm}^{-2} (where σ\sigma is the StefanBoltzmann constant). Which of the following options is/are correct?
Medium•Modern Physics
In a historical experiment to determine Planck's constant, a metal surface was irradiated with light of different wavelengths. The emitted photoelectron energies were measured by applying a stopping potential. The relevant data for the wavelength (λ)(\lambda) of incident light and the corresponding stopping potential (V0)\left(V_{0}\right) are given below :
λ(μm)\lambda(\mu \mathrm{m})V0(V_{0}( Volt ))
0.32.0
0.41.0
0.50.4
Given that c=3×108 m s−1c=3 \times 10^{8} \mathrm{~m} \mathrm{~s}^{-1} and e=1.6×10−19Ce=1.6 \times 10^{-19} \mathrm{C}, Planck's constant (in units of J sJ \mathrm{~s} ) found from such an experiment is
Medium•Modern Physics
Match the temperature of a black body given in List-I with an appropriate statement in List-II, and choose the correct option. [Given: Wien's constant as 2.9×10−3 m−K2.9 \times 10^{-3} \mathrm{~m}-\mathrm{K} and hce=1.24×10−6 V−m\frac{h c}{e}=1.24 \times 10^{-6} \mathrm{~V}-\mathrm{m} ] List-I\textbf{List-I} (P) 2000 K2000 \mathrm{~K} (Q) 3000 K3000 \mathrm{~K} (R) 5000 K5000 \mathrm{~K} (S) 10000 K10000 \mathrm{~K} List-II\textbf{List-II} (1) The radiation at peak wavelength can lead to emission of photoelectrons from a metal of work function 4eV4 \mathrm{eV}. (2) The radiation at peak wavelength is visible to human eye. (3) The radiation at peak emission wavelength will result in the widest central maximum of a single slit diffraction. (4) The power emitted per unit area is 1/161 / 16 of that emitted by a blackbody at temperature 6000 K6000 \mathrm{~K}. (5) The radiation at peak emission wavelength can be used to image human bones.
Medium•Modern Physics
Young's modulus of elasticity YY is expressed in terms of three derived quantities, namely, the gravitational constant GG, Planck's constant hh and the speed of light cc, as Y=cαhβGγY=c^{\alpha} h^{\beta} G^{\gamma}. Which of the following is the correct option?