Science (English Medium) Class 12 - CBSE Question Bank Solutions for Physics

A proton and an α-particle are accelerated, using the same potential difference. How are the de-Broglie wavelengths λp and λ_a related to each other?

Assuming an electron is confined to a 1 nm wide region, find the uncertainty in momentum using Heisenberg Uncertainty principle (∆x∆p ≃ h). You can assume the uncertainty in position ∆x as 1 nm. Assuming p ≃ ∆p, find the energy of the electron in electron volts.

Two particles A and B of de Broglie wavelengths λ₁ and λ₂ combine to form a particle C. The process conserves momentum. Find the de Broglie wavelength of the particle C. (The motion is one dimensional).

A particle A with a mass m _A is moving with a velocity v and hits a particle B (mass m_B) at rest (one dimensional motion). Find the change in the de Broglie wavelength of the particle A. Treat the collision as elastic.

For the transistor circuit shown in figure, evaluate V_E, R_B, R_E given I_C = 1 mA, V_CE = 3 V, V_BE = 0.5 V and V_CC = 12 V, β = 100.

State the two Kirchhoff’s rules used in the analysis of electric circuits and explain them.

Derive the equation of the balanced state in a Wheatstone bridge using Kirchhoff’s laws.

Read the following paragraph and answer the questions.

1. Why the image formed at infinity is often considered most suitable for viewing. Explain
2. In modern microscopes, multicomponent lenses are used for both the objective and the eyepiece. Why?
3. Write two points of difference between a compound microscope and an astronomical telescope
   OR
   Write two distinct advantages of a reflecting type telescope over a refracting type telescope.

With the help of a ray diagram explain the working of a reflecting telescope.

An alpha particle is accelerated through a potential difference of 100 V. Calculate:

1. The speed acquired by the alpha particle, and
2. The de-Broglie wavelength is associated with it.

(Take mass of alpha particle = 6.4 × 10⁻²⁷ kg)

An electron is accelerated from rest through a potential difference of 100 V. Find:

1. the wavelength associated with
2. the momentum and
3. the velocity required by the electron.

How mass defect is related to the stability of the nucleus?

Draw a labelled ray diagram showing the image formation by a refracting telescope. Define its magnifying power.

Which of the following graphs correctly represents the variation of a particle momentum with its associated de-Broglie wavelength?

• Assertion (A): The deflecting torque acting on a current-carrying loop is zero when its plane is perpendicular to the direction of the magnetic field.
• Reason (R): The deflecting torque acting on a loop of the magnetic moment `vecm` in a magnetic field `vecB` is given by the dot product of `vecm` and `vecB`.

How will the de-Broglie wavelength associated with an electron be affected when the velocity of the electron decreases? Justify your answer.

How will the de-Broglie wavelength associated with an electron be affected when the accelerating potential is increased? Justify your answer.

Draw a ray diagram for the formation of image of an object by an astronomical telescope, in normal adjustment. Obtain the expression for its magnifying power.

The magnifying power of an astronomical telescope in normal adjustment is 2.9 and the objective and the eyepiece are separated by a distance of 150 cm. Find the focal lengths of the two lenses.

A charge Q is placed at the centre of a cube. The electric flux through one of its faces is ______.