List of top Physics Questions asked in CBSE CLASS XII

A telescope has an objective lens of focal length 150 cm and an eyepiece of focal length 5 cm. Calculate its magnifying power in normal adjustment and the distance of the image formed by the objective.
Write Einstein’s photoelectric equation. How did Millikan prove the validity of this equation?
Assertion (A): Equal amount of positive and negative charges are distributed uniformly on two halves of a thin circular ring as shown in figure. The resultant electric field at the centre O of the ring is along OC.
Reason (R): It is so because the net potential at O is not zero. 
Equal amount of positive and negative charges
Four point charges of 1 \(\mu C\), -2 \(\mu C\), 1 \(\mu C\), and -2 \(\mu C\) are placed at the corners A, B, C, and D respectively, of a square of side 30 cm. Find the net force acting on a charge of 4 \(\mu C\) placed at the center of the square.
Assertion (A): The energy of a charged particle moving in a magnetic field does not change. % Reason (R) Reason (R): It is because the work done by the magnetic force on the charge moving in a magnetic field is zero.
Assertion (A): An alpha particle is moving towards a gold nucleus. The impact parameter is maximum for the scattering angle of 180°. % Reason (R) Reason (R): The impact parameter in an alpha particle scattering experiment does not depend upon the atomic number of the target nucleus.
Assertion (A): In a Young's double-slit experiment, interference pattern is not observed when two coherent sources are infinitely close to each other. % Reason (R) Reason (R): The fringe width is proportional to the separation between the two sources.
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?
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 focal lengths of the objective and the eyepiece of a compound microscope are 1 cm and 2 cm respectively. If the tube length of the microscope is 10 cm, the magnification obtained by the microscope for most suitable viewing by relaxed eye is:
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:
The electromagnetic waves used to purify water are:
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 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?
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 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:
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 the figure, a ray of light is incident on a transparent liquid contained in a thin glass box at an angle of 45° with its one face. The emergent ray passes along the face AB. Find the refractive index of the liquid.
a ray of light is incident on a transparent liquid contained in a thin glass box
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) \(\frac{\lambda}{12}\).