Lakhmir Singh solutions for फिज़िक्स [अंग्रेजी] कक्षा १० आईसीएसई chapter 12 - Modern Physics [Latest edition]

The radioisotopes find their vital use in medical and industrial fields and in scientific research. What is the tracer technique in terms of radioisotope?

What is meant by radioactivity?

What type of radiations are emitted? Explain briefly the nature of these radiations.

How is the radioactivity of an element affected when it forms chemical compounds?

How Becquerel rays, which is a combination of α, β and γ rays, be separated?

When does the nucleus of an atom tend to become radioactive?

What are isotopes?

An isotope of uranium is ₉₂Y²³⁸, i.e., it has mass number 235 and atomic number 92.

Find the number of protons and neutrons in its nucleus.

Write two similarities between an electron and a beta particle.

State any two precautions to be taken while handling radioactive substances.

Give any two important sources of background radiation.

State whether the following statement is true or false.

Beta particles are electrons of nuclear origin.

State whether the following statement is true or false.

The radioactivity of a substance decreases when kept at a very low temperature.

State whether the following statement is true or false.

With the emission of a beta particle, the mass number of the daughter nuclei increases by one.

\[\ce{_83^214Bi -> _84^214Po +}\] ______

A radioactive carbon nucleus, \[\ce{^14_6C}\] has ______ protons and ______ neutrons.

The radiation emitted from a radioactive source which has the lowest ionising power is ______.

Complete the following nuclear equation:

\[\ce{_Z^AX -> _2^4He + }\] ______

To convert \[\ce{^232_90Th}\] into \[\ce{^228_90Th}\] Th, the least number of α- and β-particles that have to be emitted are ______ and ______, respectively.

Which one of the following does not apply to radioactive radiations?

Source of nuclear waste is:

In the following radioactive equation,

\[\ce{^235_92U -> X + α -> Y + β -> Z + γ}\]

The atomic numbers of nuclei X, Y and Z are:

Ascending order of α, β and radiations with respect to their penetrating power is:

Which of the radioactive radiations can cause severe genetic disorders?

Nuclear power plants work on nuclear fission to generate heat and produce electricity. Can we create the nuclear fusion process on Earth? Can we use nuclear fusion to generate electricity?

A hydrogen bomb works on the principle of nuclear fusion that requires very high temperature. How can we trigger hydrogen to meet the conditions necessary for nuclear fusion?

Name the process used for producing electricity using nuclear energy.

Write Einstein’s mass-energy equivalence relation and calculate the nuclear energy (in MeV) released due to loss of mass by 1 amu.

 Differentiate between nuclear fission and nuclear fusion. 

Why nuclear fusion reaction is also called thermo-nuclear reaction?

State whether the following statement is true or false.

A hydrogen bomb, a mass destructive weapon works on the principle of nuclear fission.

State whether the following statement is true or false.

A controlled chain reaction occurs in a nuclear reactor.

State whether the following statement is true or false.

Nuclear fusion produces very harmful radioactive wastes.

State whether the following statement is true or false.

The harnessing of the nuclear energy in the nuclear reactor becomes possible when the number of neutrons in the immediate environment of uranium nuclei is limited by some means.

State whether the following statement is true or false.

Nuclear bombs are the result of uncontrolled chain reaction.

Artificial or induced radioactivity in stable nuclei is produced by bombarding ______ particles.

The temperature required for the process of nuclear fusion is of the order of ______ K.

The particle used in nuclear fission for bombardment is ______.

In the nuclear reaction, \[\ce{^235_92U + ^1_0n -> X + ^90_37Pb + 2^1_0n}\], the element X is:

Which of the following options is applicable for the two isotopes of uranium, \[\ce{^235_92U}\] and \[\ce{^238_92U}\]?

Which of the following is incorrect about the nuclear fission reaction?

Who invented nuclear fission?

The release of energy from the Sun is caused by ______.

True or False.

Approximately half of the background radiation is emitted by radon isotopes.

True or False.

Cobalt treatment uses the radio isotopе cobalt-60 to treat diseases, such as cancer.

True or False.

Neutrons produced in the nuclear fission initiate a chain reaction.

True or False.

Gamma radiation of a radioactive substance is electrically charged but does not deflect in the magnetic field.

True or False.

The penetrating power of β-rays is less than that of α-rays.

The mass number and atomic number of an element are not changed when it emits ______.

The ______ of a radioactive element increases by 1 unit when it emits beta particles.

During the emission of a beta particle, the ______ number remains same.

The radiation, emitted from a radioactive source, which has the most penetrating power is ______.

The radiation that goes undeviated in the electric and magnetic fields is ______.

Which among the following radiations are electromagnetic?

In mass-energy equivalence, energy equivalent to 1 amu is ______.

A nuclear fusion reaction is also called a thermonuclear reaction because ______.

Nuclear energy liberated per unit mass ______.

The energy released during an atomic explosion is due to ______.

Which of the following statements about nuclear fission is true?

1. It happens when a neutron collides with a larger atom, causing it to excite and split into two smaller atoms.
2. Radioactive products are formed during the fission process, and several neutrons are emitted.

Which among the following is used to kill cancer cells since it is an intense source of gamma radiations?

Carbon dating is utilised to ______.

Becquerel rays can:

If the radiations from a radioactive substance are deflected towards the anode in the presence of an electric field, the rays are ______.

Match the items of Column I with that of Column II and choose the appropriate code.

When does the nucleus of an atom tend to become radioactive?

State two similarities between γ-rays and X-rays.

State two dissimilarities between the γ-rays and X-rays.

What causes the emission of β-particles?

Can radioactivity be controlled?

Name the atoms of a substance having same atomic number, but different mass numbers. Give one example of such a substance. How do the structures of such atoms differ?

Suggest one effective way for the safe disposal of nuclear waste.

A certain radioactive nucleus emits a particle that leaves its mass unchanged, but increased its atomic number by one. Identify the particle and write its symbol.

Give one example of a radio isotope.

State one use of radio isotopes.

Why are alpha-particle tracks observed in a cloud chamber much shorter than beta-particle tracks, though both are emitted from the same radioactive sample and have almost the same speed?

The nucleus \[\ce{^202_84U}\] emits an a-particle and forms the nucleus Y. Represent this change in the form of an equation.

State two safety measures to be taken while establishing a nuclear power plant.

Suggest one effective way for the safe disposal of nuclear waste.

A nucleus Pu emits an alpha particle and changes to U, which emits a beta particle and then a gamma particle to change into \[\ce{^235_93Np}\]. Write the above nuclear changes in the form of an equation stating the atomic number and mass number of each nucleus.

What happens to the atomic number of an element when it emits an alpha particle.

What happens to the atomic number of an element when it emit a beta particle.

Complete the following nuclear reaction:

\[\ce{^208_84Po -> ^204_82Pb + }\] ______

Complete the following nuclear reaction:

\[\ce{^32_15P -> ^32_16S + }\] ______

A radioactive source X is shown in a thick lead-walled container with a narrow opening, as in the figure. The radiations travel through an electric field formed by the plates A and B.

1. Complete the diagram by indicating the paths of α-, β- and γ-radiations.
2. Why is the source X kept in a container with a thick lead wall and a narrow opening?

A certain nucleus X has a mass number of 16 and an atomic number of 7. Find the number of neutrons. The nucleus X emits one α-particle. Write the symbol of the new nucleus and express the change using a reaction.

A certain nucleus X has a mass number of 16 and an atomic number of 7. Find the number of neutrons. The nucleus X emits one γ-ray photon. Write the symbol of the new nucleus and express the change using a reaction.

A certain nucleus B (mass number 238 and atomic number 92) is radioactive and becomes a nucleus A (mass number 234 and atomic number 90) with the emission of a particle.

1. Name the particle emitted. Give reason.
2. State the change in the form of a nuclear reaction.

Name the radioactive radiations, which have the least penetrating.

State one use of radio isotopes.

What is mean by background radiation?

An atomic nucleus A is composed of 84 protons and 128 neutrons.

1. The nucleus A emits an alpha particle and is transformed into nucleus B. What is the composition of nucleus B?
2. The nucleus B emits a beta particle is transformed into nucleus C. What is the composition of nucleus C?
3. Does the composition of nucleus C change if it emits gamma radiations?

Represent the change in the nucleus of a radioactive element when a β particle is emitted.

What is the name given to elements with the same mass number and different atomic number?

Under which conditions does the nucleus of an atom tend to radioactive?

If 192 MeV of energy is released due to nuclear fission of each nucleus of U-235, what mass of U-235 undergoes fission per hour in a reactor of power 400 MW?

(Given, 1 amu = 1.66 × 10²⁷ kg)

Determine the amount of energy released (in MeV) due to the loss of mass of 0.5 kg.

If in nuclear fission of a piece of uranium, 0.6 g mass is lost, how much energy (in kW h) is obtained?

How many alpha and beta particles are emitted when the uranium nucleus ₉₂U²³⁸ decays to Lead If ₈₂Pb²⁰⁶?

We have learnt that every element is made up of tiny particles called atoms. Many scientists have proposed different models of the atom and were involved in the evolution of modern atomic theory. Search the Internet and create a presentation on the atomic theory timeline. Include the name and image of the scientist, name of the model, year of discovery, image of the model and any other important information about the model in the presentation.

We have learnt about the periodic table in Chemistry. Choose an element and find out its atomic number and mass number using the periodic table. Calculate the number of protons, neutrons and electrons in the element and build its 3D atomic model using ping pong balls or craft balls. Using this model,

1. learn the concept of atomic and nuclear structure
2. predict the change in the element on subtraction or addition of a proton, electron or neutron
3. understand the concept of isotopes, isobars and isotones

A nuclear power plant generates electricity through heat energy produced during nuclear fission. Create a working model of a nuclear power plant to understand the operation of the plant.