List of top Questions asked in UP Board XII

Write the Kirchhoff's law of voltage and current.
How does the p-n junction diode is used as the half wave rectifier ? Explain its working by drawing simple circuit.
An \(\alpha\)-particle accelerated by potential difference of V volt strikes with a nucleus (atomic no. = Z). If r be the nearest distance of the particle to reach the nucleus then prove that : \(r = 14.4 \frac{Z}{V} \AA\)
What is the photo-electric effect ? Write its laws. Establish the Einstein's equation of photoelectric effect \(\frac{1}{2} mv^2 = h(\nu - \nu_0)\).
The energy of electron in an excited hydrogen atom is -3.4 eV. Determine the angular momentum of this electron.
How will you detect plane polarized light by polaroid?
Electron is moving with speed of \(2 \times 10^6\) m/s in an orbit of radius \(5.0 \times 10^{-11}\) metre in hydrogen atom. Determine the magnetic moment of rotating electron.
Obtain the expression for capacity of a parallel plate capacitor. How the capacity will be increased?
Two rail tracks are isolated with each other and on the ground as well. They are connected with a milivoltmeter. What will be the reading in milivoltmeter when a train run at the speed of 180 km/hour on it? Given that the vertical component of earth's field is \(0.2 \times 10^{-4}\) weber/m\(^2\) and tracks are 1 m distance apart with each other.
What is the meaning of wavefront? Explain reflection of light by the Huygen's wave theory.
The resistance of p-n junction diode in forward bias is 25 ohm. How much voltage in forward bias be changed so that the change in current would be 2 mA?
What is meant by Wattless current? A capacitor of 15 \(\mu\)F is connected to an AC source of 220 V and 50 Hz. Find out reactance of circuit and rms value of AC current.
Write the principle and working of alternating current generator.
Write the de Broglie wavelengths in terms of kinetic energy.
Prove that total internal reflection of light ray from refracting surface is possible only when the value of angle of prism A be more than \(\sin^{-1}\left(\frac{1}{n}\right)\), where 'n' is refractive index of the material of prism.
The ratio of diameters of two copper wires of same length is 2 : 1. Compare their resistances.
What is meant by threshold wavelength in photoelectric effect?
i current is flowing in a wire shown in figure. What will be the value of magnetic field at O of semi-circle :
(i) Due to each length \(l\) of straight portion, (ii) Due to radius R of semi-circle ?
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What do you understand by coherent source?
What are the electromagnetic waves? Write down its characteristics.
In the following nuclear reaction X is
\(_{2}^{4}\text{He} + _{7}^{14}\text{N} \rightarrow _{8}^{17}\text{O} + \text{X}\)
The difference in angular momentum of electron between two successive orbits of hydrogen atom is
The force, by which the \(\alpha\)-particles are scattered in the \(\alpha\)-particle scattering experiment of Rutherford, is
The frequency range of ultraviolet radiation in electromagnetic radiation spectrum is
The sun makes an angle of 0.5\(^\circ\) on earth's surface. Its image is made with convex lens of focal length 50 cm. The diameter of image will be