The positron or antielectron(e + ) is defined as an antiparticle or the antimatter counterpart of the electron. The positron was discovered by Carl D. Anderson in the year 1932 . It has an electric charge of + 1 , a spin of 1 2 (the same as the electron), and the same mass as an electron. When a positron collides with an electron, annihilation occurs. If this collision occurs at low energies, it results in the production of two or more photons. The two main processes of production of positron are positron emission radioactive decay and pair production. The interaction between energetic photons with an atom in a material is known as pair production. Positron emission, beta plus decay, or β + decay is a subtype of radioactive decay called beta decay, in which a proton inside a radionuclide nucleus is converted into a neutron while releasing a positron and an electron neutrino( ν e ). Positron emission is mediated by a weak force. The positron is a type of beta particle( β + ), the other beta particle being the electron( β - ) emitted from the β - decay of a nucleus. An example of positron emission ( β + decay) is shown with magnesium- 23 decaying into sodium- 23 : Mg 12 23 → Na 11 23 + e + + ν e

In the decay sequence: U 92 238 → - x 1 Th 90 234 → - x 2 Pa 91 234 → - x 3 Z 234 → - x 4 Th 90 234 x 1 , x 2 , x 3 and x 4 are the particles/ radiation emitted by the respective isotopes. The correct option(s) is/are:

x 1 will deflect towards the negatively charged plate.

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Define positron.

Important Questions on Energy

EASY

Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

If the quantity of a radioactive element is doubled, the rate of disintegration will

EASY

Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

The decay constant which is the reciprocal of the time duration for which the number of the atoms of radioactive substance falls to

MEDIUM

Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

The ratio of the binding energies of three nuclei is

1 : 4 : 9

. If the ratio of their nuclear radii is

1 : 2 : 3

, the nuclei in the decreasing order of the stability can be arranged as

HARD

Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

A radioactive sample is emitting

64

times radiations than non-hazardous limit. If its half life is

2 h

, after what time it become non hazardous?

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Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

In the decay sequence:

${}_{92}^{238}U \overset{- x_{1}}{\to} {}_{90}^{234}{Th} \overset{- x_{2}}{\to} {}_{91}^{234}{Pa} \overset{- x_{3}}{\to} {}^{234}Z \overset{- x_{4}}{\to} {}_{90}^{234}{Th}$

$x_{1}, x_{2}, x_{3}$ and $x_{4}$ are the particles/ radiation emitted by the respective isotopes. The correct option(s) is/are:

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Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

Select the correct option

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Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

A nucleus

X

captures a

β

particle and then emits a neutron and

γ

ray to form

Y . X

and

Y

are:-

HARD

Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

Explain the processes of nuclear fission and nuclear fusion by using the plot of binding energy per nucleon

(B E / A)

versus the mass number

A

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Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

A bacterial infection in an internal wound grows as

N^{'} (t) = N_{0} e x p (t)

, where the time

t

is in hours. A dose of antibiotic, taken orally, needs 1 hour to reach the wound. Once it reaches there, the bacterial population goes down as

\frac{d N}{d t} = - 5 N^{2}

. What will be the plot of

\frac{N_{0}}{N}

t

after

1

hour?

HARD

Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

{}_{92}^{238}U

is known to undergo radioactive decay to form

{}_{82}^{206}{Pb}

by emitting alpha and beta particles. A rock initially contained

68 \times 10^{- 6} g

{}_{92}^{238}U

. If the number of alpha particles that it would emit during its radioactive decay of

{}_{92}^{238}U

{}_{82}^{206}{Pb}

in three half-lives is

Z \times 10^{18}

, then what is the value of

Z

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Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

{}_{93}^{239}{Np}

is a

β

-emitter, but the product is also radioactive and give

{}^{235}U

. Which particle(s) is/are emitted by the product?

EASY

Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

In the radioactive disintegration series

_{90}^{232} T h \to_{82}^{208} P b,

involving

α

and

β

decay, the total number of

α

and

β

particles emitted are

MEDIUM

Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

The particles emitted during the sequential radioactive decay of

{}^{238}U_{92}

{}^{206}{Pb}_{82}

are

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Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

In the radioactive decay process

Question Image

1. A and B are isobars

2. A and D are isotopes

3. C and D are isobars

4. A and C are isotopes

HARD

Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

Define the term ‘decay constant’ of a radioactive sample. The rate of disintegration of a given radioactive nucleus is

10000

disintegrations and

5, 000

disintegrations after

20 h o u r

. and

30 h o u r

. respectively from start. Calculate the half-life and the initial number of nuclei at

t = 0

EASY

Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

The ionisation power is maximum for:

EASY

Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

The explosion of atom bomb is based on the principle of

EASY

Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

Consider, the radioactive disintegration

{}_{82}A^{210} \to B \to C \to {}_{82}D^{206}

The sequence of emission can be

HARD

Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

In the nuclear transmutation

_{4}^{9} Be + X ⟶_{4}^{8} Be + Y

, identify

(X, Y)

MEDIUM

Chemistry>Physical Chemistry>Energy>Nuclear Fusion and Fission

^{227} A c

has a half-life of 22 years with respect to radioactive decay. The decay follows two parallel paths:

^{227} Ac \to^{227} T h

and

^{227} Ac \to^{223} F r

. If the percentage of the two daughter nuclides are

2.0

and

98.0

, respectively the decay constant (in

y e a r^{- 1}

) for

^{227} Ac \to^{227} T h

path is closest to

Define positron.

Important Questions on Energy

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