List of top Physics Questions asked in CBSE CLASS XII

Draw the graph showing the variation of scattered particles detected (\( N \)) with the scattering angle (\( \theta \)) in the Geiger-Marsden experiment. Write two conclusions that you can draw from this graph. Obtain the expression for the distance of closest approach in this experiment.

Differentiate between nuclear fission and fusion.

In normal adjustment, for a refracting telescope, the distance between the objective and eyepiece lens is 1.00 m. If the magnifying power of the telescope is 19, find the focal length of the objective and the eyepiece lens.

An air bubble is trapped at point B (CB = 20 cm) in a glass sphere of radius 40 cm and refractive index 1.5 as shown in the figure. Find the nature and position of the image of the bubble as seen by an observer at point P.

Two electric heaters have power ratings \( P_1 \) and \( P_2 \), at voltage \( V \). They are connected in series to a DC source of voltage \( V \). Find the power consumed by the combination. Will they consume the same power if connected in parallel across the same source?

A ray of light is incident normally on one face of an equilateral glass prism of refractive index \( P \). When the prism is completely immersed in a transparent medium, it is observed that the emergent ray just grazes the adjacent face. Find the refractive index of the medium.

A proton and an \( \alpha \)-particle are accelerated through different potentials \( V_1 \) and \( V_2 \) respectively so that they have the same de Broglie wavelengths. Find \( \frac{V_1}{V_2} \).

Assertion (A): In interference and diffraction of light, light energy reduces in one region producing a dark fringe. It increases in another region and produces a bright fringe.
Reason (R): This happens because energy is not conserved in the phenomena of interference and diffraction.

Assertion (A): The temperature coefficient of resistance is positive for metals and negative for p-type semiconductors.
Reason (R): The charge carriers in metals are negatively charged, whereas the majority charge carriers in p-type semiconductors are positively charged.

Assertion (A): Electrons are ejected from the surface of zinc when it is irradiated by yellow light.
Reason (R): Energy associated with a photon of yellow light is more than the work function of zinc.

In the Balmer series of the hydrogen atom, as the wavelength of spectral lines decreases, they appear:

The phase difference between electric field \( \vec{E} \) and magnetic field \( \vec{B} \) in an electromagnetic wave propagating along the z-axis is:

Figure shows the variation of inductive reactance \( X_L \) of two ideal inductors of inductance \( L_1 \) and \( L_2 \) with angular frequency \( \omega \). The value of \( \frac{L_1}{L_2} \) is:

A galvanometer of resistance 100 \( \Omega \) is converted into an ammeter of range (0 – 1 A) using a resistance of 0.1 \( \Omega \). The ammeter will show full-scale deflection for a current of about:

The magnetic susceptibility for a diamagnetic material is:

A straight wire is kept horizontally along the east-west direction. If a steady current flows in the wire from east to west, the magnetic field at a point above the wire will point towards:

The radius \( r_n \) of the \( n^{th} \) orbit in the Bohr model of the hydrogen atom varies with \( n \) as:

The quantum nature of light explains the observations on the photoelectric effect as:

A series LCR circuit connected to a variable frequency 230 V source. L = 5.0 H, C = 80mF, R = 40 Ω.

(a) Determine the source frequency which drives the circuit in resonance.

(b) Obtain the impedance of the circuit and the amplitude of current at the resonating frequency.

(c) Determine the rms potential drops across the three elements of the circuit. Show that the potential drop across the LC combination is zero at the resonating frequency

A silver wire has a resistance of 2.1 Ω at 27.5 °C, and a resistance of 2.7 Ω at 100 °C. Determine the temperature coefficient of resistivity of silver.

Show that the wavelength of electromagnetic radiation is equal to the de Broglie wavelength of its quantum (photon).

Light incident normally on a plane mirror attached to a galvanometer coil retraces backwards as shown in Fig. 9.29. A current in the coil produces a deflection of 3.5o of the mirror. What is the displacement of the reflected spot of light on a screen placed 1.5 m away?

In a parallel plate capacitor with air between the plates, each plate has an area of 6 × 10^–3 m² and the distance between the plates is 3 mm. Calculate the capacitance of the capacitor. If this capacitor is connected to a 100 V supply, what is the charge on each plate of the capacitor?

(a) A circular coil of 30 turns and radius 8.0 cm carrying a current of 6.0 A is suspended vertically in a uniform horizontal magnetic field of magnitude 1.0 T. The field lines make an angle of 60° with the normal of the coil. Calculate the magnitude of the counter torque that must be applied to prevent the coil from turning.
(b) Would your answer change, if the circular coil in (a) were replaced by a planar coil of some irregular shape that encloses the same area? (All other particulars are also unaltered.)

An object of size 3.0 cm is placed 14cm in front of a concave lens of focal length 21cm. Describe the image produced by the lens. What happens if the object is moved further away from the lens?