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

A radioactive substance disintegrates into two types of daughter nuclei, one type with disintegration constant λ₁ and the other type with disintegration constant λ₂ . Determine the half-life of the radioactive substance.

A monoenergetic (18 keV) electron beam initially in the horizontal direction is subjected to a horizontal magnetic field of 0.04 G normal to the initial direction. Estimate the up or down deflection of the beam over a distance of 30 cm (m_e = 9.11 × 10^–31 kg).

The magnetic moment vectors µ_s and µ_l associated with the intrinsic spin angular momentum S and orbital angular momentum l, respectively, of an electron are predicted by quantum theory (and verified experimentally to a high accuracy) to be given by:

µ_s = –(e/m) S,

µ_l = –(e/2m) l

Which of these relations is in accordance with the result expected classically? Outline the derivation of the classical result.

In charging by Induction, a metallic object is charged ______.

For a one dimensional electric field, the correct relation of E and potential V is _________.

A point charge + q is placed at a distance d from an isolated conducting plane. The field at a point P on the other side of the plane is ______.

Two small balls having the same mass and charge and located on the same vertical at heights h₁ and h₂ are thrown in the same direction along the horizontal at the same velocity v. The first ball touches the ground at a distance l from the initial vertical. At what height H₂ will the second ball be at this instant ? The air drag and the effect of the charges induced on the ground should be neglected.

In a parallel plate capacitor, the capacity increases if ______.

Two identical capacitors are joined in parallel, charged to a potential V, separated and then connected in series, the positive plate of one is connected to the negative of the other. Which of the following is true?

Consider an uncharged conducting sphere. A positive point charge is placed outside the sphere. The net charge on the sphere is then, ______.

A positive charge Q is uniformly distributed along a circular ring of radius R. A small test charge q is placed at the centre of the ring (figure). Then

1. If q > 0 and is displaced away from the centre in the plane of the ring, it will be pushed back towards the centre.
2. If q < 0 and is displaced away from the centre in the plane of the ring, it will never return to the centre and will continue moving till it hits the ring.
3. If q < 0, it will perform SHM for small displacement along the axis.
4. q at the centre of the ring is in an unstable equilibrium within the plane of the ring for q > 0.

A parallel plate capacitor is connected to a battery as shown in figure. Consider two situations:

1. Key K is kept closed and plates of capacitors are moved apart using insulating handle.
2. Key K is opened and plates of capacitors are moved apart using insulating handle.

Choose the correct option(s).

1. In A: Q remains same but C changes.
2. In B: V remains same but C changes.
3. In A: V remains same and hence Q changes.
4. In B: Q remains same and hence V changes.

Two charges – q each are separated by distance 2d. A third charge + q is kept at mid point O. Find potential energy of + q as a function of small distance x from O due to – q charges. Sketch P.E. v/s x and convince yourself that the charge at O is in an unstable equilibrium.

Consider a ray of light incident from air onto a slab of glass (refractive index n) of width d, at an angle θ. The phase difference between the ray reflected by the top surface of the glass and the bottom surface is ______.

Suppose we consider a large number of containers each containing initially 10000 atoms of a radioactive material with a half life of 1 year. After 1 year ______.

When a nucleus in an atom undergoes a radioactive decay, the electronic energy levels of the atom ______.

Samples of two radioactive nuclides A and B are taken. λ_A and λ_B are the disintegration constants of A and B respectively. In which of the following cases, the two samples can simultaneously have the same decay rate at any time?

1. Initial rate of decay of A is twice the initial rate of decay of B and λ_A = λ_B.
2. Initial rate of decay of A is twice the initial rate of decay of B and λ_A > λ_B.
3. Initial rate of decay of B is twice the initial rate of decay of A and λ_A > λ_B.
4. Initial rate of decay of B is the same as the rate of decay of A at t = 2h and λ_B < λ_A.