List of top Physics Questions on Modern Physics

A rod of length L is heated from temperature \( T_1 \) to \( T_2 \). Let \( T_2 - T_1 = \Delta T \) and the expansion of the rod be \( \Delta L_1 \). The rod is further heated from \( T_2 \) to \( T_3 \) such that \( T_1 + T_3 = 2T_2 \). Find the expansion of the rod \( \Delta L_2 \):

Electron and proton are accelerated with the same potential to achieve de-Broglie wavelengths of \( \lambda_1 \) and \( \lambda_2 \). Given \( m_p = 1849 \, m_e \), find the ratio \( \lambda_1/\lambda_2 \):

Find the ratio of momentum of photons of 1\textsuperscript{st and 2\textsuperscript{nd} line of Balmer series of hydrogen atom.}

Shortest wavelength of Lyman series is \(x\). Find the difference of wavelengths of first Balmer and second Balmer line in terms of \(x\).

A cube of side \(1\,\text{mm}\) is placed at centre of circular coil of radius \(10\,\text{cm}\). Current flowing in coil is \(2\,A\). Find magnetic field energy stored in cube. (\(\pi = 3.14\))

Electric field in space is given by \[ \vec{E} = 2x\hat{i} + 3y^2\hat{j} + 4\hat{k} \] A charge \(q = 3\,C\) is taken from \(r_1(0,-1,-3)\) to \(r_2(5,1,2)\). Find magnitude of \( \Delta U \).

Find minimum \(R_s\) so that LED light does not get damaged (power rating of LED is \(2\,mW\)).

For the given circuit, find the ratio of instantaneous voltage across the inductor when current is \(2\,\text{mA}\) and when current is \(4\,\text{mA}\).

Find heat dissipated in \(6\Omega\) resistance in \(100\) seconds in the given circuit.

Electric field due to a half ring at the center is \(100\,\text{N/C}\). Find the charge on the ring. Radius of the ring is \(10\,\text{cm}\).

Consider given apparatus

If a 6 kg block is released from rest as shown in the figure, then find the velocity of the 6 kg block just before hitting the ground.

A square loop of side 2 cm makes angle 60° with magnetic field \( \mathbf{B} = 0.4 \sin(300t) \, T \). Find maximum induced EMF (in mV) in loop.

If minimum deviation for an equilateral prism is \(30^\circ\), then refractive index of the prism is:

Find binding energy of \(^{12}_{6}C\). Given mass of proton \(m_p = 1.0078\,u\) and mass of neutron \(m_n = 1.0087\,u\).

An electron travelling with velocity \(v\) in free space enters a medium where its velocity is reduced by \(20\%\). The de-Broglie wavelength of the electron in the medium is \(\alpha \lambda_0\), where \(\lambda_0\) is the wavelength in free space. Find the value of \(\alpha\).

Consider the nuclear reaction: \[ {}^{2}_{1}H + {}^{2}_{1}H \rightarrow {}^{4}_{2}He \] Binding energy per nucleon of \( {}^{2}_{1}H \) and \( {}^{4}_{2}He \) are \(1.1\,\text{MeV}\) and \(7\,\text{MeV}\) respectively. Find the energy released in the nuclear reaction.

If moment of inertia of rod about axis AB is equal to moment of inertia of solid sphere about an axis parallel to AB which is at 9m from AB axis as shown in the figure. If \( R = \frac{\alpha}{2} \), then find \( \alpha \).

Nuclei \(A\) and \(B\) form a nucleus \(C\). Binding energy per nucleon for \(A, B\) and \(C\) are \(3\,\text{MeV}, 7\,\text{MeV}\) and \(6\,\text{MeV}\) respectively. Find the energy produced in the reaction: \[ 2A^{3} + B^{4} \rightarrow C^{10} \]

In hydrogen atom an electron jumps from state \(i\) to \(f\). Radius of path of electron in state \(i\) and \(f\) are \(r_i\) and \(r_f\) respectively such that \[ \frac{r_i}{r_f}=\frac{4}{1} \] If Rydberg constant \(R = 1.0976\times10^7\ \text{m^{-1}\), find wavelength of emitted photon (in \(\text{\AA}\)). (\(r_i\) and \(r_f\) are minimum possible radius.)}

Consider Bohr's model of a H-atom. If magnetic field at center due to electron in 2\(^n\) orbit is \( B_1 \), and magnetic field due to electron in 4\(^t\) orbit is \( B_2 \). Find \( \frac{B_1}{B_2} \).

Nuclei \(A\) and \(B\) form a nucleus \(C\). The binding energy per nucleon (BE/N) for \(A\), \(B\), and \(C\) are \(3\,\text{MeV}\), \(7\,\text{MeV}\), and \(6\,\text{MeV}\) respectively. Find the energy produced in the reaction: \[ 2A^3 + B^4 \rightarrow C^{10} \]