Physics M.C.Q (1 Marks)

Assertio : Hydrogen atom consists of only one electron but its emission spectrum has many lines.  

Reason  : Only Lyman series is found in the absorption spectrum of hydrogen atom whereas in the emission spectrum, all the series are found.

The rest energy of an electron is 0.511 MeV. The electron is accelerated from rest to a velocity 0.5 c. The change in its energy will be

The binding energy per nucleon of  is 7.97 MeV and that of  is 7.75 MeV. The energy (in MeV)  required to remove a neutron from  is

The sun radiates energy in all directions. The average radiations received on the earth surface from the sun is .The average earth- sun distance is 1.5 . The mass lost by the sun per day is (1 day = 86400 seconds)

If the atom   follows the Bohr model and the radius of   is n times the Bohr radius, then find n

The wavelengths involved in the spectrum of deuterium  are slightly different from that of hydrogen spectrum, because

In the Bohr model of the hydrogen atom, let R, v and E represent the radius of the orbit, the speed of electron and the total energy of the electron respectively. Which of the following quantity is proportional to the quantum number n

An electron passing through a potential difference of 4.9 V collides with a mercury atom and transfers it to the first excited state. What is the wavelength of a photon corresponding to the transition of the mercury atom to its normal state

A neutron with velocity V strikes a stationary deuterium atom, its kinetic energy changes by a factor of

The ionisation potential of H-atom is 13.6 V. When it is excited from ground state by monochromatic radiations of 970.6  the number of emission lines will be (according to Bohr’s theory)

A double charged lithium atom is equivalent to hydrogen whose atomic number is 3. The wavelength of required radiation for emitting electron from first to third Bohr orbit in   will be (Ionisation energy of hydrogen atom is 13.6eV)

If in Rutherford’s experiment, the number of particles scattered at 90° angle are 28 per min, then number of scattered particles at an angle 60°  and 120°  will be

What is the radius of iodine atom (at. no. 53, mass number 126)

In a hypothetical Bohr hydrogen, the mass of the electron is doubled. The energy  and the radius  of the first orbit will be ( is the Bohr radius)

A radioactive material has a half-life of 8 years. The activity of the material will decrease to about 1/8 of its original value in

A hydrogen atom in its ground state absorbs 10.2 eV of energy. The orbital angular momentum is increased by (Given Planck constant h = 6.6 J - sec)

A hydrogen atom in its ground state absorbs 10.2 eV of energy. The orbital angular momentum is increased by

An energy of 24.6 eV is required to remove one of the electrons from a neutral helium atom. The energy (in eV) required to remove both the electrons from a neutral helium atom is

A sodium atom is in one of the states labeled 'Lowest excited levels'. It remains in that state for an average time of 10^–8 sec, before it makes a transition back to a ground state. What is the uncertainty in energy of that excited state

In hydrogen atom, electron makes transition from n=4 to n=1 level. Recoil momentum of the H atom will be

In a sample of radioactive material, what fraction of the initial number of active nuclei will remain undisintegrated after half of a half-life of the sample

In a radioactive reaction  , the number of α - particles emitted is

If half life of radium is 77 days. Its decay constant in day will be

The phenomenon of radioactivity is

 In this reaction how many α  and β  particles are emitted

 has half life 5700 years. At the end of 11400 years, the actual amount left is

Nuclear fusion is common to the pair

The particle that possesses half integral spin as

A nucleus of mass 218 amu in free state decays to emit an a-particle. Kinetic energy of the a-particle emitted is 6.7 MeV. The recoil energy (in MeV) of the daughter nucleus is

The composition of an a -particle  can be expressed as

The ratio of the speed of the electrons in the ground state of hydrogen to the speed of light in vacuum is

Mean life of a radioactive sample is 100 seconds. Then its half life (in minutes) is

an isotope of thorium decays in ten stages emitting six a-particles and four b-particles in all. The end product of the decay is

A nucleus decays by  emission followed by a gamma emission. If the atomic and mass numbers of the parent nucleus are Z and A respectively, the corresponding numbers for the daughter nucleus are respectively.

The ratio activity of an element becomes 1/64^th of its original value in 60 sec. Then the half life period is

The half-life of a radioactive substance is 3.6 days. How much of 20 mg of this radioactive substance will remain after 36 days

The half-life of radium is about 1600 years. Of 100 g of radium existing now, 25 g will remain unchanged after

A radioactive decay chain starts from and produces     by successive emissions. The emitted particles can be

(a) Two a-particles and one b-particle

(b) Three   particles

(c) One a particle and two   particles

(d) One a particle and two   particles

The curve between the activity A of a radioactive sample and the number of active atoms N is

The charge density in a nucleus varies with distance from the centre of the nucleus according to the curve in Fig.

A count rate meter shows a count of 240 per minute from a given radioactive source. One hour later the meter shows a count rate of 30 per minute. The half-life of the source is

Radioactive nuclei that are injected into a patient collect at certain sites within its body, undergoing radioactive decay and emitting electromagnetic radiation. These radiations can then be recorded by a detector. This procedure provides an important diagnostic tool called

A radioactive sample at any instant has its disintegration rate 5000 disintegration per minute. After 5 minutes, the rate is 1250 disintegrations per minute. Then, the decay constant (per minute) is

Which of the following radiations has the least wavelength

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

Which of the following rays are not electromagnetic waves

A radioactive substance has an average life of 5 hours. In a time of 5 hours          

The half-life of   is 100μs. The time taken for the radioactivity of a sample of   to decay to 1/16^th of its initial value is

Nucleus produced due to a-decay of the nucleus   is

The activity of a sample of a radioactive material is A, at time  and  at time . If  its mean life T, then