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(a) – (iv) 

(b) – (ii) 

(c) – (iii) 

(d) – (i)

Velocity of light = 3 × 10⁸ m/s 

Mass defect Δm = 4 × 10^-3 

By Einstein’s equation, energy released 

E = mC² 

= (4 × 10^-3) × (3 × 10⁸)² 

= 36 × 10¹³ J 

= 3.6 × 10¹⁴ J

In ₄Be⁹ + ₂He⁴ → X is ₆C¹³

Correct answer is (b) ₂He⁴, ₀n¹

(i) ₄Be⁹ + ₂He⁴ → ₆C¹³ [α = ₂He⁴]

∴ X = ₆C¹³

(ii) ₉₂U²³⁵ + ₀n¹ → ₅₀Ba¹⁴¹ + Y + 3₀n¹

Equating atomic number on both sides we get, 

235 + 1 = 141 + A + 3 

236 = 144 + A 

∴ A = 236 – 144 

= 92 

Equating atomic number on both sides are get 

92 + 0 = 56 + 2 + 0 

Z = 92 – 56 = 36

∴ Y is ₃₆K⁹²

(a) – (v) 

(b) – (iv) 

(c) – (i) 

(d) – (ii)

Correct answer is (d) +2e^-

(b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.

(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.

1. 1.6 × 10¹⁵ disintegrations / second 

2. antiparticle [₁e⁰] 

3. Radio iron Fe⁵⁹ 

4. International Commission on Radiological Protection 

5. Dosimeter 

6. Gama rays 

7. X is _-1e⁰ 

8. gamma 

9. 3.84 × 10¹²J 

10. 10⁷ to 10⁹ K

11. Radio phosphorus P – 32 

12. fatal diseases like leukemia.

(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.

One roentgen is defined as the quantity of radioactive substance which produces a charge of 2.58 × 10^-4 coulomb in 1 kg of air under standard conditions of pressure, temperature and humidity.

Gamma rays are electromagnetic waves consisting of photons.

The radio isotope of phosphorous (P-32) helps to increase the productivity of crops. The radiations from the radio isotopes can be used to kill the insects and parasites and prevent the wastage of agricultural products.

The minimum mass of fissile material necessary to sustain the chain reaction is called 'critical mass (m_c)'. It depends on the nature, density and the size of the fissile material.

The first nuclear reactor was built in 1942 at Chicago, USA.

Correct answer is (c) Lead

Fusion reaction that takes place in the cores of the Sun and other stars results in an enormous amount of energy, which is called stellar energy.

The SI unit of radioactivity is becquerel.

The intensity of X-rays is very low. So, X-rays do not produce any severe effects. There are certains clothes that can be used while operating X-ray machines. Ramu can use them and so he may not be severely affected by Xrays, he should avoid eating and drinking when he is working with X-rays.

(d) mass energy relation

Hydrogen bomb is based on the principle of nuclear fusion. A hydrogen bomb is always designed to have an inbuilt atom bomb which creates the high temperature and pressure required for fusion when it explodes. Then, fusion takes place in the hydrogen core and leads to the release of a very large amount of energy in an uncontrolled manner. The energy released in a hydrogen bomb (or fusion bomb) is much higher than that released in an atom bomb (or fission bomb).

Lead protects us from radiation.

(d) 250 mR per week.

600 R of radiation that may cause death of a person when exposed to it ?

Boron and alumninum

1eV = 1.602 × 10^-19 joule

1. Radio – Iodine (I¹³¹) is used to cure goitre. 

2. Radioactive materials should be kept in a thick-walled lead container. 

3. Lead coated aprons and lead gloves should be used while working with hazardous radioactive materials. 

4. We should avoid eating while handling radioactive materials. 

5. The radioactive materials should be handled only by tongs or by a remote control device. 

6. Dosimeters should be worn by the users to check the level of radiation.

 The average energy release from a single fission process is = 200 MeV.

Gamma rays are the electromagnetic radiation which is emitted during natural radioactivity.

There are some radioactive elements, which can be converted into fissionable material. They are called as fertile materials. 

Eg: Uranium – 238, Thorium – 232, Plutonium – 240.

Element C with atomic number 235 is suitable for making atom bomb. 

\(_Z X^A \overset{\alpha}{\longrightarrow} _{101} Rf^{259}\)

Mass number A = 259 + 4 = 263

Atomic number Z = 104 + 2 = 106

Natural uranium consists of 99.28 % of ₉₂U²³⁸ and 0.72 % of ₉₂U²³⁵

A chain reaction is a self-propagating process in which the number of neutrons goes on multiplying rapidly almost in a geometrical progression.

Nuclear fusion is possible only at an extremely high temperature of the order of 10⁷ to 10⁹ K and a high pressure to push the hydrogen nuclei closer to fuse with each other. Hence, it is named as ‘Thermonuclear reaction’.

The process in which two lighter nuclei combine to form a heavier nucleus is termed as ‘nuclear fusion’.

Eg: ₁H² + ₁H² → ₂He⁴ + Q (Energy)

Fission is nuclear chain reaction. 

It is not easy to start a fusion reaction as to fuse HYDROGEN atom minimum temperature of 1000000 °C is required which is not possible to create in laboratory. Controlled fusion reaction is not possible so far.

ISOTOPES of ELEMENT HYDROGEN are : 

¹ ₁H protium 

² ₁H deuterium 

³ ₁H Tritium

Nuclear Fusion 

1. Two light nuclei fuse to form a heavy nucleus. 

2. Cannot be controlled to generate electricity position. 

Nuclear Fission 

1. A heavy nucleus splits to form two smaller nuclei. 

2. Can be controlled and is used to generate electricity.

(a) isotopes 

(a) simultaneously α, β and γ radiations

β-RADIATION is similar to a beam of electrons.

For safety, the radiations α, β and γ emitted by the radioactive sample should not come out of the sphere, αparticles have a less penetrating power and therefore, the walls of the sphere easily stop them. β-particles will not he stopped by the walls and there will be no absorption of β particles inside the sphere as the air has been withdrawn from it. The number of β particles reaching per unit area at the surface of sphere will depend on the radius of sphere. This number will be reduced to 1/4, if the radius is doubled. So some safety is obtained if the sphere is large. 

γ-radiations are also not absorbed by the walls.Thus for safety, the container should have lead walls and it should not be evacuated. The air will help in absorbing the radiations.Thus for safety, the container should have lead walls and it should not be evacuated. The air will help in absorbing the radiations.

(d) α and γ or β and γ

Discovery of radium, Radioactivity, Artifical radioactivity, Nuclear reactor.