Physics M.C.Q (1 Marks)

Assertion : For the scattering of a-particles at a large angles, only the nucleus of the atom is responsible.
Reason : Nucleus is very heavy in comparison to electrons.

Assertion : Electron capture occurs more often than positron emission in heavy elements.
Reason : Heavy elements exhibit radioactivity.

Assertion : The mass of b-particles when they are emitted is higher than the mass of electrons obtained by other means.
Reason : b-particle and electron, both are similar particles.

Assertion : The ionising power of b-particle is less compared to a-particles but their penetrating power is more.
Reason : The mass of b-particle is less than the mass of a-particle.

Assertion : Amongst alpha, beta and gamma rays, a-particle has maximum penetrating power.
Reason : The alpha particle is heavier than beta and gamma rays.

Assertion : All the radioactive elements are ultimately converted in lead.
Reason : All the elements above lead are unstable.

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.

Assertion : The electron in the hydrogen atom passes from energy level n = 4 to the n = 1 level. The maximum and minimum number of photon that can be emitted are six and one respectively.
Reason : The photons are emitted when electron make a transition from the higher energy state to the lower energy state.

Assertion : According to classical theory, the proposed path of an electron in Rutherford atom model will be parabolic.
Reason : According to electromagnetic theory an accelerated particle continuously emits radiation.

Assertion : The force of repulsion between atomic nucleus and a-particle varies with distance according to inverse square law.
Reason : Rutherford did a-particle scattering experiment.

Assertion : Isobars are the element having same mass number but different atomic number.
Reason : Neutrons and protons are present inside nucleus.

Assertion : Density of all the nuclei is same.
Reason : Radius of nucleus is directly proportional to the cube root of mass number.

Assertion : Bohr had to postulate that the electrons in stationary orbits around the nucleus do not radiate.
Reason : According to classical physics all moving electrons radiate.

Assertion : Neutrons penetrate matter more readily as compared to protons.
Reason : Neutrons are slightly more massive than protons.

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.

In Fig. X represents time and Y represent activity of a radioactive sample. Then the activity of sample, varies with time according to the curve

The graph between the instantaneous concentration (N) of a radioactive element and time (t) is

Binding energy per nucleon verses mass number curve for nuclei is shown in the figure. W, X, Y and Z are four nuclei indicated on the curve. The process that would release energy is

The fraction f of radioactive material that has decayed in time t, varies with time t. The correct variation is given by the curve

Binding energy per nucleon plot against the mass number for stable nuclei is shown in the figure. Which curve is correct

Rest mass energy of an electron is 0.54 MeV. If velocity of the electron is 0.8 c, then K.E. of the electron is

If 10% of a radioactive material decays in 5 days, then the amount of original material left after 20 days is approximately

A hydrogen like atom of atomic number Z is in an excited state of quantum number 2n. It can emit a maximum energy photon of 204 eV. If it makes a transition to quantum state n, a photon of energy 40.8 eV is emitted. The value of n will be

The first excited state of hydrogen atom is 10.2 eV above its ground state. The temperature is needed to excite hydrogen atoms to first excited level, is

Excitation energy of a hydrogen like ion in its first excitation state is 40.8 eV. Energy needed to remove the electron from the ion in ground state is

After 280 days, the activity of a radioactive sample is 6000 dps. The activity reduces to 3000 dps after another 140 days. The initial activity of the sample in dps is

Half life of a radio-active substance is 20 minutes. The time between 20% and 80% decay will be

A and B are two radioactive substances whose half lives are 1 and 2 years respectively. Initially 10 gm of A and 1 gm of B is taken. The time (approximate) after which they will have same quantity remaining is

The graph which represents the correct variation of logarithm of activity (log A) versus time, in figure is

Half-life of a radioactive substance is 20 minutes. Difference between points of time when it is 33% disintegrated and 67% disintegrated is approximately

A radioactive nucleus undergoes a-emission to form a stable element. What will be the recoil velocity of the daughter nucleus if V is the velocity of a-emission and A is the atomic mass of radioactive nucleus

The half-life of radioactive Polonium (Po) is 138.6 days. For ten lakh Polonium atoms, the number of disintegrations in 24 hours is