Unit 18 Atomic and Nuclear Physics (Short Questions)
Q.2 Write the particles present in a nucleus.
Q.3 Define isotopes and give example.
Q.4 Define Natural and artificial Radio Activity.
Q.5 Write the causes of background radiations.
Q.6 What is meant by Nuclear Transmutation?
Q.7 Write two characteristics of alpha particles.
Q.8 Write any two properties of beta particles.
Q.10 Define penetrating power of radiation.
Q.11 What is meant by Ionization and Penetrating power?
Q.12 Write half life of Hydrogen, Lead, Uranium and carbon.
Q.13 How long would it take for complete decay of a pure radioactive atom?
Q.14 What is difference between stable and unstable elements?
Q.15 Define radioactive elements.
Q.16 Write two uses of radio Isotopes in research.
Q.18 What is fission chain reaction?
Q.19 Define nuclear fusion and write its equation.
Q.20 Describe the safety measures to avoid the hazards or radiations.
Q.21 Define atom and write its basic particles.
Q.22 Differentiate between atomic number and atomic mass number.
Q.23 What is meant by background radiation?
Q.24 What is meant by Cosmic Radiation?
Q.25 What is difference between daughter and parents elements?
Q.26 Explain gamma rays with the help of examples.
Q.27 What is Photon?
Q.28 Write two properties of’ Gamma rays.
Q.29 Write two characteristics of gamma rays.
Q.30 Define half life and write half life of’ 
.
Q.31 What is meant by unstable nuclei? Explain.
Q.32 Write two uses of’ Radio Isotopes.
Q.33 What are Tracers?
Q.34 Write equation of’ nuclear fission reaction.
Q.1 What is neutron number?
Ans. Neutron Number: Number of Neutrons in nucleus is called neutron number. It is denoted by letter N.
Q.2 Write the particles present in a nucleus.
Ans: The nucleus contains protons and neutrons which are collectively called nucleons. The positive charge in an atom is concentrated in a reign called nucleus.
Q.3 Define isotopes and give example.
Ans. Isotopes: Isotopes are atoms of an element which have same number of protons but different number of neutrons in their nuclei.
Example
The Isotopes of Hydrogen are:
ii) Deuterium 
iii) Trituim 
Q.4 Define Natural and artificial Radio Activity.
Ans. Natural Radio Activity: The spontaneous emission of radiation by unstable nuclei is called natural radioactivity. The elements which emit such radiations are called radioactive element
Q.5 Write the causes of background radiations.
Ans. Background Radiations: Radiations present in the atmosphere due to different radioactive substances are called background radiations,
Causes: Every where in rocks, soil, water and air of earth are traces of radioactive elements due to which these radiations are present.
Q.6 What is meant by Nuclear Transmutation?
Ans. Nuclear Transmutation: The spontaneous process in which a parent unstable nuclei change into a more stable daughter nuclei with the emission of radiations is called nuclear transmutation.
Q.7 Write two characteristics of alpha particles.
Ans. Properties of alpha radiations:
- Alpha particle is helium nucleus comprising of two protons and two neutrons and two protons.
- The charge on that particle is 2e.
- An unstable nucleus with large protons and neutrons.
- May decay by emitting alpha radiations.
- Alpha particle has a range of only a few centimeters in air.
- The alpha particle has strong ionizing power.
Q.8 Write any two properties of beta particles.
Ans. Characteristics of Beta Radiations:
Beta radiation is a stream of high-energy electron. An unstable nuclei with excess of neutrons may eject beta radiations. The beta radiations strongly interact with matter due its charge and have a short-range a compared to gamma radiations. The speed of Beta particle is nearly equal to speed of light. Beta particles
have range of several meters in air.
Q.9 Define Ionization.
Ans. Ionization: The phenomenon by which radiation split matter into positive and negative ions is called ionization. Alpha particles have the greatest power of ionization as compared to beta particles and gamma rays.
Q.10 Define penetrating power of radiation.
Ans. Penetrating power: The strength of radiation to penetrating a certain material is called penetrating power.
Explanation: The alpha particle has the shortest range because of its strong integrating or ionizing power. The gamma rays can penetrate a considerable thickness of concrete. The beta radiations have range greater than alpha particles.
Q.11 What is meant by Ionization and Penetrating power?
Ans. Penetrating Power: The ability of radiations to penetrate a certain material is called penetrating power.
Ionizing: The phenomenon by which radiations split matter into positive and negative ions is called ionization.
Q.12 Write half life of Hydrogen, Lead, Uranium and carbon.
Ans. Hydrogen: The half life of hydrogen isotope 
is 12.3 years.
Lead: The half life of lead isotope 
is 10.6 hours.
Uranium: The half life of uranium isotopes 
is 7.1 X 108 years and half life of uranium isotope is 4.51 x 109 years.
Carbon: The half life of carbon isotope is 5730 years.
Q.13 How long would it take for complete decay of a pure radioactive atom?
Ans. Infinite time required for complete decay of a pure radioactive atom, because after every half life the remaining number of atom half and so on.
Q.14 What is difference between stable and unstable elements?
Ans. Unstable Elements
Those elements which emit radiations naturally are called unstable elements. All elements whose atomic mass is more than 82 are naturally unstable
and converted into other elements.
Stable Elements: Those nuclei which can’t emit radiations naturally are called stable elements. It atomic mass is between 1 and 82.
Q.15 Define radioactive elements.
Ans. Radioactive elements: The elements which emit radiations naturally are called radioactive elements. The atomic number of radioactive elements is
greater than 82.
Q.16 Write two uses of radio Isotopes in research.
Ans. Uses of Radio Isotopes
i. Radioactive cobalt-30 (Co-60) is used for curing cancerous tumors and cells.
ii) The age of a tree can be calculated by comparing radio activity of carbon- 14 (C-14).
Q.17 Define Carbon Dating.
Ans. Carbon Dating: When a tree dies, the radio Carbon-14 present inside the plant starts decaying. Since the half-life of Carbon-14 is,5730 years, the
age of a dead tree can be calculated by comparing the activity of carbon-14 in the live and dead tree. This process is called Carbon dating.
Q.18 What is fission chain reaction?
Ans. Fission Chain Reaction: We have seen that neutrons are emitted when U-235 undergoes fission. These neutrons can in turn trigger other nuclei to undergo fission with the possibility of a chain reaction.
Q.19 Define nuclear fusion and write its equation.
Ans. Nuclear Fusion: When two light nucleus continue to from a heavier nucleus the process is called nuclear fusion.
Q.20 Describe the safety measures to avoid the hazards or radiations.
Ans. Safety measures to avoid the radiations: We cannot detect radiations directly; we should strictly follow safety precautions, even when the radioactive sources are very weak. ‘
i. The sources should only be handled with tongs and forceps.
ii. The user should use rubber gloves and hands should be washed carefully after the experiment.
iii. All radioactive sources should be stored in thick lead containers.
iv. Never point of radioactive source towards a person.
Q.21 Define atom and write its basic particles.
Ans. Atom: Atom is an indivisible particle of matter.
Basic Particle: An atom consists of nucleus contains proton and neutron, while electrons revolve in nearly circular orbits about the positively charged nucleus.
Q.22 Differentiate between atomic number and atomic mass number.
Ans. Atomic Number: The number of protons presented inside a nucleus is called the charge number or the atomic number.
Symbol: It is denoted by the letter Z.
Atomic Mass Number: The sun of neutrons and. protons presented in a nucleus is called its atomic mass number.
Symbol: It is denoted by the letter A.
Q.23 What is meant by background radiation?
Ans. Background radiation: Radiations present in atmosphere due to different radioactive substance are called background radiations.
Q.24 What is meant by Cosmic Radiation?
Ans. Cosmic Radiation: The cosmic radiation interacts with atoms in the atmosphere to create a shower of secondary radiation, including X-rays, muons, protons, alpha particles, electrons and neutrons.
Q.25 What is difference between daughter and parents elements?
Ans. Daughter:
The elements obtained by parents elements are called daughter elements. Parents: The elements from which radiations are emits are caned parents elements.
Q.26 Explain gamma rays with the help of examples.
Ans. General Equation
Normally gamma rays reduce radiation with alpha or beta particles.
Q.27 What is Photon?
Ans. An energy packet whose energy is always quantized is called Photon.
Q.28 Write two properties of’ Gamma rays.
Properties of Gamma rays:
i. These are electromagnetic radiation of very short wavelength.
ii. Gamma rays can penetrate at least 30 cm of lead or 2 kilometer of air.
Q.29 Write two characteristics of gamma rays.
Ans. Characteristics of gamma rays are following:
i. Gamma rays are of short wavelength electromagnetic radiations.
ii. The wavelengths and energies of gamma rays can vary.
Q.30 Define half life and write half life of’ .
Ans. Half life:
The time during which half life of the unstable radioactive nuclei disintegrate is called the half-life of the sample of radioactive element.
Example
Different elements has different half life has 5730 years half life and radium-226 has 1620 year half life.
Q.31 What is meant by unstable nuclei? Explain.
Ans. Unstable nuclei: Those elements which emit radiations naturally are caned unstable elements.
All elements whose atomic mass is more than 82 are naturally unstable and converted into other elements.
Q.32 Write two uses of’ Radio Isotopes.
Ans. Uses of’ Radio Isotopes:
i. Radioisotopes are used in nuclear medicines for curing various diseases. For example, radioactive cobalt-60 is used for curing cancerous tumors and cells.
ii. These are used as tracers in medical, industry and agriculture.
Q.33 What are Tracers?
Tracers: Radioactive tracers are chemical compounds containing some quantity of radioisotope.
Example: Radio iodine-131 readily accumulates in the thyroid gland and can be used for monitoring of thyroid gland. For the diagnosis of brain tumor phosphorous-32 is used.
Q.34 Write equation of’ nuclear fission reaction.
Ans. Fission Reaction: Nuclear fission takes place when a heavy nucleus, such as U-235, split, or fissions, into two smaller nuclei by absorbing a slow
moving (low-energy) neutron.
Equation
