Taking the Bohr radius as a₀ = 53pm, the radius of Li⁺⁺ ion its ground state, on the basis of Boh''s model, will be about

O₂ molecule consists of two oxygen atoms.In the molecule, nuclear force between the nuclei of the two atoms

The Bohr model for the spectre of a H-atom

The Balmer series for the H-atom can be observed

The activity of a freshly prepared radioactive sample is \({ 10 }^{ 10 }\)  disintegrations per second, whose mean life is \({ 10 }^{ 9 }s.\) The mass of an atom of this radioisotope is \({ 10 }^{ -25 }kg.\) The mass (in mg) of the radioactive sample is :

The mass number of a nucleus is :

A deutron is bombarded on \(_{ 8 }{ { O }^{ 16 } }\) nucleus and an \(\alpha \) particle is emitted. The product nucleus is 

In the Bohr model of the hydrogen atom, let R, V and E represent the radius of the orbit, speed of the \({ e }^{ - }\) and total energy of the \({ e }^{ - }\) respectively. Which of the following quantities are proportional to the quantum number n?

A sample of a radioactive element has a mass of 10 g at an instant t = 0. The approximate mass of this element in the sample after two mean lives is

According to Thomson model, the entire mass and positive charge of an atom are distributed ____________ in a ___________ of radius ___________.

Lyman series lies in __________ region and Balmer series lies in ________ region of hydrogen spectrum.

Orbital velocity of electron in outer orbit is ____________ as compared to its value in____________.

Isotopes of an element are the atoms ___________ which have __________ but ___________.

Radioactivity is the property by virtue of which ___________ without being forced by ___________.

For a given impact parameter b, does the angle of deflection increase or decrease with increase in energy?

Two nuclei have mass numbers in the ratio 2:5. What is the ratio of their nuclear densities?

Show that the decay rate R of a sample of radionuclide is related to the number of radioactive nuclei N at the same instant by the expression \(R=\lambda N\).

Draw a plot of BE/A versus mass number A for Use this graph to explain the release of enegry in the process of nuclear fusion of two light nuclei.

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

'The half life \(_{ 6 }^{ 14 }{ C }\) is 5700 years.' What does it mean ?
Two radioactive nuclei X and Y initially contain an equal number of atoms. Their half life is 1 hour and 2 hours respectively. Calculate the ratio of their rates of disintegration after two hours.

(a) Using the Bohr's model, calculate the speed of the electron in a hydrogen atom in the n = 1, 2, and 3 levels
(b) Calculate orbital period in each of these levels.

What is Bohr's frequency condition?

Find the effective mass of a photon if the frequency of the radiation is \(6\times { 10 }^{ 14 }Hz\) .

The nuclear radius of \(_{ 8 }{ { O }^{ 16 } }\) is \(3\times { 10 }^{ -15 }m\) . What is its nuclear mass density?

A nuclear reactor is a powerful device, wherein nuclear energy is utilised for peaceful purposes. It is based upon controlled nuclear chain reaction. The nuclear chain reaction is controlled by the use of control rods (of boron or cadmium) and moderators like heavy water, graphite, etc. The whole reactor is protected with concrete walls 2 to 2.5 metre thick, so that radiations emitted during nuclear reactions may not produce harmful effects.
Read the above passage and answer the following questions:
(i) Give any two merits of nuclear reactors.
(ii) What is radiactive waste?
(iii) Why do people often oppose the location site of a nuclear reactor? What do you suggest?

Poonam's mother is diagnosed cancer. The attending physician told her that she has to undergo radiotherapy. While telling her the side effects of the treatment, the doctor told that her beautiful hair may fall and she may become bald. Poonam's mother refuses to get the treatment.
Read the above passage and answer the following questions:
(i) What would you do if you were in Poonam's place?
(ii) What values are associated with your attitude?