List of top Questions asked in UP Board XII- 2026

In which region of the electromagnetic spectrum does the Lyman series of hydrogen lie?

When a convex lens is dipped in water, its focal length and nature become:

A force of 80 newton acts between two point charges placed in air at a fixed distance. When the same charges are placed at the same distance in a dielectric medium, the force becomes 8 newton. The dielectric constant of the medium is:

In the resonance condition, the current drawn from the source by a parallel resonant (L-C) circuit is:

Write the Bohr's postulates for hydrogen atom. How did Bohr remove the drawbacks of Rutherford's model of atom?
OR
Derive the formula for the electric field outside a charged hollow sphere with the help of Gauss's law.

Explain full wave rectifying action of p-n junction diode with the help of circuit diagram.
OR
Draw the diffraction pattern of light due to single slit and write the expression for position of minima. On what factors does the width of central maxima depend?

What is the meaning of wavefront? Explain the laws of reflection on the basis of Huygens' principle of wavefront.
OR
Determine the following for the given A.C. circuit: (i) impedance, (ii) power factor, and (iii) phase difference between voltage and current. (Series combination of resistance \( R = 500\ \Omega \), inductance \( L = 10\ \text{H} \) and capacitance \( C = 20\ \mu\text{F} \) connected to an A.C. source \( V = 200\sin 100t \).)

What do you understand by electromagnetic induction? State the Faraday's laws of electromagnetic induction.
OR
Obtain the formula for the capacitance of a parallel plate capacitor when a dielectric medium is partially filled between its plates.

The energy of hydrogen atom in ground state \( (n = 1) \) is \( -13.6 \) eV. To which highest energy-state the hydrogen atom can be made to reach by the photon of energy \( 12.09 \) eV?
OR
What is meant by interference? Write the conditions for constructive and destructive interference.

What is meant by mutual inductance? Define coefficient of mutual inductance and write its unit.

Prove that the electric potential energy per unit volume of a charged condenser is \(\tfrac{1}{2}\varepsilon_0 E^2\), where symbols have their usual meaning.

What are electromagnetic waves? Draw their propagation diagram. Show the electric field amplitude and magnetic field amplitude in the propagation diagram.

The focal length of a glass \((n_g = 3/2)\) plano-convex lens in air is 10 cm. What will be the focal length and its nature when it is immersed in carbon disulphide \((n_c = 5/3)\)?

The distance between any two sources of light is 24 cm. Determine where a convergent lens of focal length 9 cm be placed so that the image of both sources be formed at one point.

Explain nuclear fission and nuclear fusion with examples.

Deduce the formula of force acting between two parallel current carrying conductors.

Resistance of a wire is \( R \). If the length of the wire is stretched by \( n \) times the original length, then what will be the new resistance of the wire?

What do you understand by free electron and drift velocity? Deduce Ohm's law on the basis of the principle of drift velocity.

Two point charges \( +10\,\mu C \) and \( -10\,\mu C \) are situated 2 cm apart. This dipole is placed in a uniform electric field of \( 1\times10^{5} \) volt/metre. Calculate the energy required to rotate the dipole from the position of \( 0^\circ \) to \( 180^\circ \).

Draw a graph between voltage and current of a p-n junction diode in forward bias.

Define mass defect and binding energy.