Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions

An electron in a hydrogen atom makes transitions from orbits of higher energies to orbits of lower energies.

1. When will such transitions result in (a) Lyman (b) Balmer series?
2. Find the ratio of the longest wavelength in the Lyman series to the shortest wavelength in the Balmer series.

The work function of a metal is 4.50 eV. Find the frequency of light to be used to eject electrons from the metal surface with a maximum kinetic energy of 6.06 × 10⁻¹⁹ J.

Monochromatic light of wavelength 600 nm is incident from the air on a water surface. The refractive index of water is 1.33. Find the

1. wavelength,
2. frequency and
3. speed, of reflected and refracted light.

A ray of monochromatic light propagating in the air is incident on the surface of the water. Which of the following will be the same for the reflected and refracted rays?

Two cells of emf E₁ and E₂ and internal resistances r₁ and r₂ are connected in parallel, with their terminals of the same polarity connected together. Obtain an expression for the equivalent emf of the combination.

An electric dipole of dipole moment 2 × 10^-8 C-m in a uniform electric field experiences a maximum torque of 6 × 10^-4 N-m. The magnitude of the electric field is ______.

An electric dipole of length 2 cm is placed at an angle of 30° with an electric field 2 × 10⁵ N/C. If the dipole experiences a torque of 8 × 10^-3 Nm, the magnitude of either charge of the dipole is ______.

An infinite line charge produces a field of 9 × 10⁴ N/C at a distance of 2 cm. Calculate the linear charge density.

Draw a schematic ray diagram of a reflecting telescope showing how rays coming from a distant object are received at the eyepiece.

Draw a labeled ray diagram to obtain the real image formed by an astronomical telescope in normal adjustment position. Define its magnifying power.

Three identical polaroid sheets P₁, P₂ and P₃ are oriented so that the pass axis of P₂ and P₃ are inclined at angles of 60° and 90° respectively with the pass axis of P₁. A monochromatic source S of unpolarised light of intensity I₀ is kept in front of the polaroid sheet P₁ as shown in the figure. Determine the intensities of light as observed by the observer at O, when polaroid P₃ is rotated with respect to P₂ at angles θ = 30° and 60°.

State the two Kirchhoff’s rules used in electric networks. How are there rules justified?

What dose a polaroid consist of?

Show, using a simple polaroid, that light waves are transverse in nature. Intensity of light coming out of a polaroid does not change irrespective of the orientation of the pass axis of the polaroid. Explain why.

State and explain Gauss’s law.

Why does an unpolarised light incident on a polaroid get linearly polarised ?

A proton and an α-particle have the same de-Broglie wavelength Determine the ratio of  their speeds.

Find an expression for intensity of transmitted light when a polaroid sheet is rotated between two crossed polaroids. In which position of the polaroid sheet will the transmitted intensity be maximum?

Use Kirchhoff's rules to obtain conditions for the balance condition in a Wheatstone bridge.

How does one demonstrate, using a suitable diagram, that unpolarised light when passed through a Polaroid gets polarised?