List of practice Questions

A beam of light coming parallel to the principal axis of a convex lens \( L_1 \) of focal length 16 cm is incident on it. Another convex lens \( L_2 \) of focal length 12 cm is placed coaxially at a distance 40 cm from \( L_1 \). The nature and distance of the final image from \( L_2 \) will be:

A thin convex lens \( L \) of focal length 10 cm and a concave mirror \( M \) of focal length 15 cm are placed coaxially 40 cm apart as shown in the figure. A beam of light coming parallel to the principal axis is incident on the lens. The final image will be formed at a distance of: 

The focal length of an equiconvex lens:

A thin converging lens of focal length 20 cm and a thin diverging lens of focal length 15 cm are placed coaxially in contact. The power of the combination is:

An AC voltage \( V = 0.5 \sin (100\pi t) \) volt is applied, in turn, across a half-wave rectifier and a full-wave rectifier. The frequency of the output voltage across them respectively will be:

Initially, during the formation of a p-n junction:

During the formation of a p-n junction:

At a given temperature, the number of intrinsic charge carriers in a semiconductor is \( 2.0 \times 10^{10} \) cm\(^{-3}\). It is doped with pentavalent impurity atoms. As a result, the number of holes in it becomes \( 8 \times 10^3 \) cm\(^{-3}\). The number of electrons in the semiconductor is:

When Ge is doped with a pentavalent impurity, the energy required to free the weakly bound electron from the dopant is about:

What are ferromagnetic materials? Explain ferromagnetism with the help of suitable diagrams, using the concept of magnetic domains.

Define mutual inductance. Write its SI unit.

Name the electromagnetic waves with their wavelength range which are used for:
(i) FM radio broadcast
(ii) Detection of fracture in bones
(iii) Treatment of muscular strain

A circular loop of radius 10 cm carrying current of 1.0 A lies in the x-y plane. A long straight wire lies in the same plane parallel to the x-axis at a distance of 20 cm as shown in the figure. 

Find the direction and value of current that has to be maintained in the wire so that the net magnetic field at O is zero. 
 

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): When electrons drift in a conductor, it does not mean that all free electrons in the conductor are moving in the same direction.
Reason (R): The drift velocity is superposed over large random velocities of electrons.

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: