Science (English Medium) कक्षा १२ - CBSE Important Questions for Physics

Using Rutherford's model of the atom, derive the expression for the total energy of the electron in hydrogen atom. What is the significance of total negative energy possessed by the electron?

Using Bohr's postulates of the atomic model, derive the expression for radius of n^th electron orbit. Hence obtain the expression for Bohr's radius.

Suppose you are given a chance to repeat the alpha-particle scattering experiment using a thin sheet of solid hydrogen in place of the gold foil. (Hydrogen is a solid at temperatures below 14 K.) What results do you expect?

Define the distance of closest approach. An α-particle of kinetic energy 'K' is bombarded on a thin gold foil. The distance of the closest approach is 'r'. What will be the distance of closest approach for an α-particle of double the kinetic energy?

Write the expression for the de Broglie wavelength associated with a charged particle having charge ‘q’ and mass ‘m’, when it is accelerated by a potential V.

Using Bohr’s postulates, derive the expression for the frequency of radiation emitted when electron in hydrogen atom undergoes transition from higher energy state (quantum number n_i) to the lower state, (n_f).

When electron in hydrogen atom jumps from energy state n_i = 4 to n_f = 3, 2, 1, identify the spectral series to which the emission lines belong.

Using Bohr’s second postulate of quantization of orbital angular momentum show that the circumference of the electron in the n^th orbital state in hydrogen atom is n times the de Broglie wavelength associated with it.

The electron in hydrogen atom is initially in the third excited state. What is the maximum number of spectral lines which can be emitted when it finally moves to the ground state?

What is meant by ionisation energy?

The diagram shows the four energy levels of an electron in the Bohr model of the hydrogen atom. Identify the transition in which the emitted photon will have the highest energy.

The radius of the n^th orbit in the Bohr model of hydrogen is proportional to ______.

In the study of Geiger-Marsdon experiment on scattering of α particles by a thin foil of gold, draw the trajectory of α-particles in the coulomb field of target nucleus. Explain briefly how one gets the information on the size of the nucleus from this study.

From the relation R = R₀ A^1/3, where R₀ is constant and A is the mass number of the nucleus, show that nuclear matter density is independent of A

Write symbolically the process expressing the β⁺ decay of `""_11^22Na`. Also write the basic nuclear process underlying this decay.

Is the nucleus formed in the decay of the nucleus `""_11^22Na`, an isotope or isobar?

Why is it found experimentally difficult to detect neutrinos in nuclear β-decay?

A radioactive nucleus 'A' undergoes a series of decays as given below:

The mass number and atomic number of A₂ are 176 and 71 respectively. Determine the mass and atomic numbers of A₄ and A.

Define the activity of a given radioactive substance. Write its S.I. unit.

Draw the plot of binding energy per nucleon (BE/A) as a functino of mass number A. Write two important conclusions that can be drawn regarding the nature of nuclear force.

Use this graph to explain the release of energy in both the processes of nuclear fusion and fission.

Write the basic nuclear process of neutron undergoing β-decay.