List of top Questions asked in UP Board XII

Calculate the energy of a \( \text{He}^+ (Z = 2) \) in its first excited state.
Define drift velocity of free electrons and write the relation between drift velocity and current density.
Obtain the formula for the electric potential on the axial line of an electric dipole.
What are matter waves? Write de Broglie equation.
Define critical angle. Explain working of optical fibre.
The work function of a metal is \( 2.5 \times 10^{-9} \) joule. If the metal is exposed to a light beam of frequency \( 6.0 \times 10^{14} \) Hz, what will be the stopping potential?
In a transistor:
The net resistance of an ammeter should be small to ensure that:
Write the minimum orbital angular momentum of the electron in a hydrogen atom.
Define optical centre of a lens.
As compared to \(^{12}_6C\) atom, how many extra protons and neutrons does the \(^{14}_6C\) atom have?
How much energy is released in mass defect of 1 amu?
The electric field of intensity \( \vec{E} = (3 \hat{i} + 4 \hat{j}) \, \text{N/C} \) passes through the plane of area \( \vec{A} = (10 \hat{i}) \, \text{m}^2 \). Find the electric flux.
What do you understand by electromagnetic induction? State Faraday’s laws regarding electromagnetic induction.
What is the meaning of wavefront? Explain the laws of reflection by explaining Huygens' principle of wavefront.
What is LED? Explain its principle, construction and working.
The equation \( E = pc \), where \( E \), \( p \), and \( c \) represent energy, momentum, and velocity of light, is valid:
As the temperature of a metal and of a semiconductor is increased, the:
The equivalent resistance of the network shown in figure between A and B is:
Obtain the formula for refractive index of material of prism in terms of angle of minimum deviation and angle of prism.
Explain both the laws of Kirchhoff of electrical circuits.
What is the meaning of matter-wave of Louis de Broglie? Deduce the relation for wavelength of de Broglie in terms of kinetic energy.
Derive the formula for the capacitance of a parallel plate capacitor, partially filled with a dielectric.
What is a transistor? By drawing the circuit diagram of common emitter configuration, plot the output characteristics.
Define the formula for the resonant frequency in a series L-C-R alternating current circuit.