List of top Questions asked in CBSE CLASS XII

The variation of the stopping potential \( V_0 \) with the frequency \( \nu \) of the incident radiation for four metals A, B, C, and D is shown in the figure. For the same frequency of incident radiation producing photo-electrons in all metals, the kinetic energy of photo-electrons will be maximum for which metal?
variation of the stopping potential
The energy of an electron in the ground state of hydrogen atom is -13.6 eV. The kinetic and potential energy of the electron in the first excited state will be:
A Young’s double-slit experimental setup is kept in a medium of refractive index \( \frac{4}{3} \). Which maximum in this case will coincide with the 6th maximum obtained if the medium is replaced by air?
A pure Si crystal having \( 5 \times 10^{28} \) atoms m\(^{-3}\) is doped with 1 ppm concentration of antimony. If the concentration of holes in the doped crystal is found to be \( 4.5 \times 10^9 \) m\(^{-3}\), the concentration (in m\(^{-3}\)) of intrinsic charge carriers in the Si crystal is about:
A particle of mass \( m \) and charge \( q \) describes a circular path of radius \( R \) in a magnetic field. If its mass and charge were \( 2m \) and \( \frac{q}{2} \) respectively, the radius of its path would be:
Which of the following pairs is that of paramagnetic materials?
A galvanometer of resistance 50 \( \Omega \) is converted into a voltmeter of range (0 — 2V) using a resistor of 1.0 k\( \Omega \). If it is to be converted into a voltmeter of range (0 — 10 V), the resistance required will be:
Two coils are placed near each other. When the current in one coil is changed at the rate of 5 A/s, an emf of 2 mV is induced in the other. The mutual inductance of the two coils is:
A charge \( +Q \) is placed on a thin conducting spherical shell of radius \( r \). Derive an expression for the electric field at a point lying (i) inside and (ii) outside the shell.
Show that the electric field for the same charge density \(\sigma\) is twice in case of a conducting plate or surface than in a nonconducting sheet.
A galvanometer of resistance \( G \) is converted into a voltmeter of range \( (0 - V) \) by using a resistance \( R \). Find the resistance, in terms of \( R \) and \( G \), required to convert it into a voltmeter of range \( (0 - \frac{V}{2}) \).
A rectangular coil of \(N\) turns and area of cross-section \(A\) is rotated at a steady angular speed \(\omega\) in a uniform magnetic field. Obtain an expression for the emf induced in the coil at any instant of time.
Two coplanar and concentric circular loops \( L_1 \) and \( L_2 \) are placed coaxially with their centres coinciding. The radii of \( L_1 \) and \( L_2 \) are 1 cm and 100 cm respectively. Calculate the mutual inductance of the loops. (Take \( \pi^2 = 10 \))
Trace the path of a ray of light showing refraction through a triangular prism and hence obtain an expression for the angle of deviation (\(\delta\)) in terms of \(A\), \(i\), and \(e\), where symbols have their usual meanings. Draw a graph showing the variation of the angle of deviation with the angle of incidence.
In Young’s double slit experiment, find the ratio of intensities at two points on a screen when waves emanating from two slits reaching these points have path differences (i) \(\frac{\lambda}{6}\) and (ii) \(\frac{\lambda}{12}\).
The displacement of two light waves, each of amplitude 'a' and frequency \(\omega\), emanating from two coherent sources of light, are given by \(y_1 = a \cos(\omega t)\) and \(y_2 = a \cos(\omega t + \phi)\). \(\phi\) is the phase difference between the two waves. These light waves superpose at a point. Obtain the expression for the resultant intensity at that point.
The magnetic flux through a coil of resistance 5 \(\Omega\) increases with time as: \(\Phi = (2.0 t^3 + 5.0 t^2 + 6.0 t)\) mWb. Find the magnitude of induced current through the coil at \(t = 2\) s.
The number of bright fringes formed due to interference on 1 m of screen placed at \(\frac{4}{3}\) m away from the slits is:
Obtain the expression for the capacitance of a parallel plate capacitor with a dielectric medium between its plates.
The number of peaks of the interference fringes formed within the central peak of the envelope of the diffraction pattern will be:
The number of peaks of the interference formed if the slit width is doubled while keeping the distance between the slits same will be:
If instead of 450 nm light, another light of wavelength 680 nm is used, the number of peaks of the interference formed in the central peak of the envelope of the diffraction pattern will be:
Consider the diffraction of light by a single slit described in this case study. The first minimum falls at an angle equal to:
The figure shows four pairs of parallel identical conducting plates, separated by the same distance of 2.0 cm and arranged perpendicular to the x-axis. The electric potential of each plate is mentioned
parallel identical conducting plates
(i) For which pair of the plates is the electric field E alongˆ i?
Let \(E_1\), \(E_2\), \(E_3\), and \(E_4\) be the magnitudes of the electric field between the pairs of plates, I, II, III, and IV respectively. Then: