CBSE Class 12 Physics VBQs Atoms and Nuclei

CBSE Class 12 Physics VBQs Atoms and Nuclei Set B read and download in pdf. Value Based Questions come in exams for Physics in Standard 12 and are easy to learn and helpful in scoring good marks. You can refer to more chapter wise VBQs for Class 12 Physics and also get latest topic wise very useful study material as per latest 2021 NCERT book for Class 12 Physics and all other subjects for free on Studiestoday designed as per latest Grade 12 CBSE, NCERT and KVS syllabus and examination pattern

Atoms and Nuclei

 

One Marks Question

Question. What is the ratio of the nuclear densities of two nuclei having mass number in the ratio of 1:4?
Answer : Nuclear density is independent of mass number so ratio will be 1:1

Question. Which has greater ionizing power:- alpha or beta particle?
Answer : Alpha Particle.

Question. In Bohr’s theory of model of a Hydrogen atom, name the physical quantity which equals to an integral multiple of h/2Π
Answer : Angular momentum

Question. What is the relation between ‘n’ & radius ‘r’ of the orbit of electron in a Hydrogen atom according to Bohr’s theory?
Answer : r α n2

Question. Among the alpha, beta & gamma radiations, which are the one affected by a magnetic field?
Answer : alpha & beta

Two Marks questions:

Question. Why nuclear force is not possible in laboratory?
Answer : It require very high temperature to carry on so not possible.

Question. What is the difference between an electron and a beta particle?
Answer :  An electron coming from nucleus is called beta particle.

Question. Define half-life and mean life of a radioactive substance and its relation.
Answer : Time during which one half of the initial nuclei disintegrates, ratio of combined age of total number of atom present in the given sample. Mean life =144* half life

Question. Explain the emission of gamma ray with example.
Answer :  Emission of gamma ray by the de excitation of nucleus, cobalt 

Question. Write two properties of alpha particles.
Answer :  They are reflected by electric and magnetic field, absorbed by matter, velocity one by 10 th of velocity of light, ionizes gases. 

THREE MARKS QUESTION:

Question. Define the terms:- Half-life period and Decay constant of a radioactive sample. Derive the relation between these terms.
Answer :  Half-life Period : The half-life period of an element is defined as the time in which the number of radioactive nuclei decay to half of its initial value. The decay constant of a radioactive element is defined as the reciprocal of time in which the number of undecided nuclei of that radioactive element falls to be1/e times of its initial value.

Question. Explain the observations and significance of Rutherford Alpha particle scattering experiment.
Answer :  Most of the alpha particle passes undefleted, a few deflected at different angles. 

Question. State Bohr’s postulate for explaining the spectrum of hydrogen atom.
Answer : Electrons moves in a fixed orbit, angular momentum is quantized, electrons are revolving in stationary orbits, energy emitted is the difference between the two levels of orbits.

Question. State Displacement law for radioactive decay.
Answer : Rate of nuclear disintegration is directly proportional to the no. of decayed particles




Value Based Questions

Question 1. Ruchi’s uncle who was a kabadiwalah was getting weak day by day. His nails were getting blue, he stated losing his hair. This happened immediately after he purchased a big container of heavy mass from Delhi University Chemistry Department. Doctors advised him hospitalization and suspected he has been exposed to radiation. His uncle didn’t know much about radiations but Ruchi immediately convinced her uncle to get admitted and start treatment.

(i) What according to you are the values utilized by Rama to convince her uncle to get admitted in hospital

(ii) Name the radioactive radiations emitted from a radioactive element

Answer:
 
(i) Value displayed - awareness, critical thinking, decision making
 
(i) X ray and Gamma rays.
 
 
Question 2. Medha’s grandfather was reading article is newspaper. He read that after so many years of atomic bombing is Hiroshima or Nagasaki, Japan National census indicated that children born even now are genetically deformed. His grandfather was not able to understand the reason behind it. He asked his Granddaughter Medha who is studying in class XII science. Medha sat with her grandfather and showed him pictures from some books and explained the harmful effects of radiations.

(i) What are the values/ skills utilized by kajal to make her grandfather understand the reason of genetically deformity?

(ii) Name the nuclear reactions that occurred is atom bomb.

Answer:

(i) Sympathy, compassion
 
(ii) Nuclear- fission reactions
 
 
Question 3. Muthuswami a resident of Kundakulam was all set to leave everything and shift to another place in view of the decision of Govt. to start nuclear thermal power plant at Kundakulam. His granddaughter Prachi, a science student, was really upset on the ignorant decision of her grandfather. She could finally convince him not to shift, since adequate safety measures to avoid any nuclear mishap have already been taken by the Govt. before starting nuclear thermal plants.
• What is the value displayed by Prachi in convincing her grandfather
• What is the principle behind working of nuclear reactor
• What are the main components of nuclear reactor
• Why is heavy water used as moderator?

Answer:

(i) Awareness, social responsibility
 
(ii) Controlled chain reaction
 
(iii) Nuclear Fuel, Moderator, Control rods, Coolant, Shielding
 
(iv) Neutrons produced during fission get slowed if they collide with a nucleus of same mass. As ordinary water contains hydrogen atoms so it can be used as a moderator. But it absorb neutron at a fast rate. To overcome this difficulty, Heavy waters is used as a moderator which has negligible cross sections for neutron absorption

 

Value Based Questions:

Question 1. Ruchi’s uncle who was a kabadiwalah was getting weak day by day. His nails were getting blue, he stated losing his hair. This happened immediately after he purchased a big container of heavy
mass from Delhi University Chemistry Department. Doctors advised him hospitalization and
suspected he has been exposed to radiation. His uncle didn’t know much about radiations but
Ruchi immediately convinced her uncle to get admitted and start treatment.

(i) What according to you are the values utilized by Rama to convince her uncle to get admitted in hospital

(ii) Name the radioactive radiations emitted from a radioactive element

Answer:

(i) Value displayed - awareness, critical thinking, decision making

(ii) X ray and Gamma rays.

 

Question 2. Medha’s grandfather was reading article is newspaper. He read that after so many years of atomic bombing is Hiroshima or Nagasaki, Japan National census indicated that children born even now are genetically deformed. His grandfather was not able to understand the reason behind it. He asked his Granddaughter Medha who is studying in class XII science. Medha sat with her grandfather and showed him pictures from some books and explained the harmful effects of radiations.

(i) What are the values/ skills utilized by kajal to make her grandfather understand the reason of genetically deformity?

(ii) Name the nuclear reactions that occurred is atom bomb.

Answer:

(i) Sympathy, compassion

(ii) Nuclear- fission reactions

 

Question 3. Muthuswami a resident of Kundakulam was all set to leave everything and shift to another place in view of the decision of Govt. to start nuclear thermal power plant at Kundakulam. His granddaughter Prachi, a science student, was really upset on the ignorant decision of her grandfather. She could finally convince him not to shift, since adequate safety measures to avoid any nuclear mishap have already been taken by the Govt. before starting nuclear thermal plants.
• What is the value displayed by Prachi in convincing her grandfather
• What is the principle behind working of nuclear reactor
• What are the main components of nuclear reactor
• Why is heavy water used as moderator?

Answer:

(i) Awareness, social responsibility

(ii) Controlled chain reaction

(iii) Nuclear Fuel, Moderator, Control rods, Coolant, Shielding

(iv) Neutrons produced during fission get slowed if they collide with a nucleus of same mass. As ordinary water contains hydrogen atoms so it can be used as a moderator. But it absorb neutron at a fast rate. To overcome this difficulty, Heavy waters is used as a moderator which has negligible cross sections for neutron absorption

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