CBSE 12 Physics Question Paper-2023 Set-2

A steady current is flowing through a metallic wire of non-uniform cross-sectional area (A) which is continuously increasing from one end to another. The drift velocity of the free electrons as a function of 'A' is:

An Assertion (A) and a Reason (R) are given below. For the statements, choose the correct answer from the given options:
Assertion (A): The magnetic field is always a closed loop.
Reason (R): The magnetic lines of force do not have a beginning or an end.
Choose the correct answer:

If the energy band gap between the valence band and conduction band is 6 eV, then the semiconductor is a/an:

The ratio of the de Broglie wavelength of an electron and a proton, if they have the same kinetic energy is:

The peak value of the a.c. source is 4A. The value of the current shown by a hot-wire ammeter will be:

The ratio of the energy of a photon of wavelength 4000 Å to the energy of a photon of wavelength 2000 Å is:

A ray of light is incident normally on a plane mirror. The angle of reflection will be:

A proton enters a uniform magnetic field of flux density 1 T with a velocity 10^7 m s-1 at an angle of 30° to the field. The radius of the helical path followed by the proton is approximately:

A proton and an electron are moving in a straight line with the same speed. The ratio of their de Broglie wavelengths (λp/λe) is approximately:

If a coil is connected to a d.c. source, its resistance:

The ratio of the energy of a photon of 2000 Å to the energy of a photon of 4000 Å is:

A convex lens is placed in contact with a concave lens. The focal length of the convex lens is 20 cm and that of the concave lens is -20 cm. The combination acts as a:

For a radioactive sample, the fraction of the initial number of nuclei that remains undecayed after 4 half-lives is:

The electric potential at a point on the equatorial line of a short electric dipole is:

The ratio of the wavelengths of a photon and an electron, if they have the same momentum is:

In the energy band diagram of n-type Si, the order of the gap between the bottom of the conduction band Ec and the donor energy level Ed is:

The force F→ is experienced by a point charge situated on the axis of a short electric dipole at a distance 'r' from it. If the distance of the charge is made 2r, the force experienced by the charge will be:

The correct graph representing the variation of resistance R with temperature T for a metallic conductor is:

Electromagnetic waves of wavelength 6000 Å fall on an opaque surface. The work function of the surface is 1.24 eV. The kinetic energy of the emitted photoelectrons will be:

The potential difference across the terminals of a cell in an open circuit is 8V. The potential difference drops to 4V when a current of 4A is drawn from it. The internal resistance of the cell is:

The internal resistance of a cell is found to be 2 Ω. If a current of 2 A is drawn from it, the terminal potential difference of the cell is 6 V. The e.m.f. of the cell is:

The direction of the vector E→ × B→ in an electromagnetic wave is:

An Assertion (A) and a Reason (R) are given below. For the statements, choose the correct answer from the given options:
Assertion (A): The resistivity of a semiconductor increases with increase in temperature.
Reason (R): The energy gap is very small in semiconductors.
Choose the correct answer:

In a nuclear reaction, an element X undergoes a decay to an element Y, as shown: X₉₂ → Y₉₀ + He₂. The element X emits:

The de Broglie wavelength of an electron moving with speed c/2 is:

An Assertion (A) and a Reason (R) are given below. For the statements, choose the correct answer from the given options:
Assertion (A): An equiconvex lens made of glass with refractive index 1.5 has the same focal length as the radius of curvature of one of its faces.
Reason (R): For an equiconvex lens, R₁ = -R₂ = R.
Choose the correct answer:

In a p-n junction diode, the holes are created by the:

Which of the following is correct for a forward biased p-n junction?

An Assertion (A) and a Reason (R) are given below. For the statements, choose the correct answer from the given options:
Assertion (A): The emission of a photon takes place when an electron in a higher energy orbit jumps to a lower energy orbit.
Reason (R): The energy of the electron in the higher energy orbit is less than that in the lower energy orbit.
Choose the correct answer:

The ratio of the magnitude of the force acting on a point charge on the axis of a short electric dipole at distance r to the force acting on it at a distance 2r is:

If a coil of insulated wire is connected to a battery, its resistance:

The current in the circuit shown in the figure is:

The velocity of electromagnetic waves in a medium with relative permittivity εr and relative permeability μr is: