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

The count rate of 10g of radioactive material was measured at different times and this has been shown in the figure. The half life of material and the total counts (approximately) in the first half life period, respectively are

For a substance the average life for a-emission is 1620 years and for b emission is 405 years. After how much time the 1/4 of the material remains after a and b emission

The half life period of a radioactive element X is same as the mean life time of another radioactive element Y. Initially both of them have the same number of atoms. Then

A freshly prepared radioactive sample of half- life 1 hour emits radiations that are 128 times as intense as the permissible safe limit. The minimum time after which this sample can be safely used is

A radioactive material decays by simultaneous emission of two particles with respective half lives 1620 and 810 years. The time (in years) after which one- fourth of the material remains is

From a newly formed radioactive substance (Half life 2 hours), the intensity of radiation is 64 times the permissible safe level. The minimum time after which work can be done safely from this source is

A nucleus with mass number 220 initially at rest emits an a-particle. If the Q value of the reaction is 5.5 MeV, calculate the kinetic energy of the a-particle

The rest mass of an electron as well as that of positron is 0.51 MeV. When an electron and positron are annihilate, they produce gamma-rays of wavelength(s)

For uranium nucleus how does its mass vary with volume

A heavy nucleus at rest breaks into two fragments which fly off with velocities in the ratio 8 : 1. The ratio of radii of the fragments is

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

Which of the following atoms has the lowest ionization potential

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

The transition from the state n = 4 to n = 3 in a hydrogen-like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition

Imagine an atom made up of a proton and a hypothetical particle of double the mass of the electron but having the same charge as the electron. Apply the Boh’r atom model and consider all possible transitions of this hypothetical particle to the first excited level. The longest wavelength photon that will be emitted has wavelength l (given in terms of the Rydberg constant R for the hydrogen atom) equal to

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

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)

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

The number of revolutions per second made by an electron in the first Bohr orbit of hydrogen atom is of the order of 3

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

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

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

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

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

The phenomenon of radioactivity 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 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 a radioactive substance is 40 years. How long will it take to reduce to one fourth of its original amount and what is the value of decay constant

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

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

Carbon dating is best suited for determining the age of fossils if their age in years is of the order of

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

A radioactive substance emits

During mean life of a radioactive element, the fraction that disintegrates is

Three fourth of the active decays in a radioactive sample in 3/4 sec. The half life of the sample is 

A radioactive material has an initial amount 16gm. After 120 days it reduces to 1gm, then the half-life of radioactive material is

The S.I. unit of radioactivity is

In a sample of radioactive material, what percentage of the initial number of active nuclei will decay during one mean life

10 gm of radioactive material of half-life 15 year is kept in store for 20 years. The disintegrated material is

Certain radio-active substance reduces to 25% of its value in 16 days. Its half-life is

1 mg gold undergoes decay with 2.7 days half-life period, amount left after 8.1 days is

99% of a radioactive element will decay between

A radioactive nucleus with Z protons and N neutrons emits an a-particle, 2b-particles and 2 gamma rays. The number of protons and neutrons in the nucleus left after the decay respectively, are

A radioactive nucleus emits a beta particle. The parent and daughter nuclei are

Half-life is measured by

During negative b - decay

When a radioactive substance emits an a -particle, its position in the periodic table is lowered by

The electron emitted in beta radiation originates from

1 Curie is equal to

A radio isotope has a half life of 75 years. The fraction of the atoms of this material that would decay in 150 years will be

If half-life of a radioactive atom is 2.3 days, then its decay constant would be

In a mean life of a radioactive sample

The activity of a radioactive sample is 1.6 curie and its half-life is 2.5 days. Its activity after 10 days will be

What fraction of a radioactive material will get disintegrated in a period of two half-lives

After five half lives what will be the fraction of initial substance
 

If half-life of a substance is 3.8 days and its quantity is 10.38 gm. Then substance quantity remaining left after 19 days will be

A radioactive sample has half-life of 5 years. Probability of decay in 10 years will be

The activity of a radioactive sample

A radioactive substance has a half-life of 1 year. The fraction of this material, that would remain after 5 years will be

In beta decay

The large scale destruction, that would be caused due to the use of nuclear weapons is called

A radioactive substance emits

Plutonium decays with a half-life of 24000 years. If the plutonium is stored for 72000 years, then the fraction of plutonium that remains is

3.8 days is the half-life period of a sample. After how many days, the sample will become 1/8th of the original substance

The half-life of radon is 3.8 days. Three forth of a radon sample decay in

Consider the following two statements
A. Energy spectrum of a-particles emitted in radioactive decay is discrete
B. Energy spectrum of b-particles emitted in radioactive decay is continuous

The activity of a radioactive sample is measured as 9750 counts per minute at t = 0 and as 975 counts per minute at t = 5 minutes. The decay constant is approximately

Decay constant of radium is λ. By a suitable process its compound radium bromide is obtained. The decay constant of radium bromide will be

Which of the following isotopes is used for the treatment of cancer

At any instant the ratio of the amount of radioactive substances is 2 : 1. If their half lives be respectively 12 and 16 hours, then after two days, what will be the ratio of the substances

A radioactive sample with a half life of 1 month has the label : “Activity=2 micro curies on 1.8.1991.'' What will be its activity two months later

In the given nuclear reaction A, B, C, D, E represents ​​​​​​​ ​​​​​​​ ​​​​​​​ 

Half life of a radioactive element is 10 days. The time during which quantity remains 1/10 of initial mass will be

The particles emitted by radioactive decay are deflected by magnetic field. The particles will be

In the disintegration series the values of Z and A respectively will be

Which of the following statements are true regarding radioactivity
(I) All radioactive elements decay exponentially with time
(II) Half life time of a radioactive element is time required for one half of the radioactive atoms to disintegrate
(III) Age of earth can be determined with the help of radioactive dating
(IV) Half life time of a radioactive element is 50% of its average life period
Select correct answer using the codes given below
Codes :

An atom of mass number 15 and atomic number 7 captures an α - particle and then emits a proton. The mass number and atomic number of the resulting product will respectively be

Half lives of two radioactive substances A and B are respectively 20 minutes and 40 minutes. Initially the sample of A and B have equal number of nuclei. After 80 minutes, the ratio of remaining number of A and B nuclei is

Which of the following is a correct statement

After 1α and 2β emissions

The half life period of a radioactive substance is 5 min. The amount of substance decayed in 20 min will be

The half life (T) and the disintegration constant (λ) of a radioactive substance are related as

The rate of disintegration of fixed quantity of a radioactive element can be increased by

In a radioactive decay, neither the atomic number nor the mass number changes. Which of the following would be emitted in the decay process

The radioactive decay of uranium into thorium is expressed by the equation where ‘X’ is

The counting rate observed from a radioactive source at t = 0 second was 1600 counts per second and at t = 8 seconds it was 100 counts per second. The counting rate observed, as counts per second at t = 6 seconds, will be

N atoms of a radioactive element emit n alpha particles per second. The half life of the element is

A element used for radioactive carbon dating for more than 5600 years is

A radioactive substance has a half life of 60 minutes. After 3 hours, the fraction of atom that have decayed would be

Unit of radioactivity is Rutherford. Its value is

16 gm sample of a radioactive element is taken from Bombay to Delhi in 2 hour and it was found that 1 gm of the element remained (undisintegrated). Half life of the element is

If 20 gm of a radioactive substance due to radioactive decay reduces to 10 gm in 4 minutes, then in what time 80 gm of the same substance will reduce to 10 gm

Consider a radioactive material of half-life 1.0 minute. If one of the nuclei decays now, the next one will decay(a) (b)(c) (d)

The decay constant of a radioactive element is 0.01 per second. Its half life period is

A radioactive element emits 200 particles per second. After three hours 25 particles per second are emitted. The half life period of element will be

The correct order of ionizing capacity of α, β and γ - rays is

The half life of polonium is 140 days. After how many days, 16 gm polonium will be reduced to 1 gm (or 15g will decay)

Which can pass through 20 cm thickness of the steel

Some radioactive nucleus may emit

Curie is a unit of

A radio-isotope has a half- life of 5 years. The fraction of the atoms of this material that would decay in 15 years will be

A sample contains 16 gm of a radioactive material, the half life of which is two days. After 32 days, the amount of radioactive material left in the sample is

Atomic mass number of an element thorium is 232 and its atomic number is 90. The end product of this radioactive element is an isotope of lead (atomic mass 208 and atomic number 82). The number of alpha and beta particles emitted is

Which of the following is not a mode of radioactive decay

Half life of radioactive element depends upon

Radioactivity is

If the decay or disintegration constant of a radioactive substance is λ, then its half life and mean life are respectively
 

In which radioactive disintegration, neutron dissociates into proton and electron