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ISC (Science) ISC Class 12 - CISCE Important Questions

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What is the velocity of an electron in the 3rd orbit of hydrogen atom if its velocity in the 1st orbit is v0?

Appears in 1 question paper
Chapter: [12] Atoms
Concept: Bohr’s Model for Hydrogen Atom

Radius of the 1st orbit of hydrogen atom is r0. What will be the radius of the 4th orbit?

Appears in 1 question paper
Chapter: [12] Atoms
Concept: Alpha-particle Scattering and Rutherford’s Nuclear Model of Atom

The de Broglie wavelength of an electron in the first Bohr’s orbit of hydrogen atom is equal to ______.

Appears in 1 question paper
Chapter: [12] Atoms
Concept: Bohr’s Model for Hydrogen Atom

During Rutherford’s gold foil experiment, it was observed that most of the α-particles did not deflect. However, some showed a deflection of 180°. 

What hypothesis was made to justify the deflection of α-particle by 180°?

Appears in 1 question paper
Chapter: [12] Atoms
Concept: Alpha-particle Scattering and Rutherford’s Nuclear Model of Atom

Name a material which is used in making control rods in a nuclear reactor.

Appears in 1 question paper
Chapter: [13] Nuclei
Concept: Atomic Masses and Composition of Nucleus

Write one balanced equation to show Nuclear fusion

Appears in 1 question paper
Chapter: [13] Nuclei
Concept: Nuclear Fusion

Write one balanced equation to show Emission of `beta^-` (i.e. a negative beta particle)

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Chapter: [13] Nuclei
Concept: Atomic Masses and Composition of Nucleus

With the help of a suitable example and an equation, explain the term pair production.

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Chapter: [13] Nuclei
Concept: Atomic Masses and Composition of Nucleus

Write one balanced reaction representing nuclear fusion.

Appears in 1 question paper
Chapter: [13] Nuclei
Concept: Nuclear Fusion

In a nuclear reactor, what is the function of a moderator?

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Chapter: [13] Nuclei
Concept: Nuclear Fusion

In our Nature, where is the nuclear fusion reaction taking place continuously?

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Chapter: [13] Nuclei
Concept: Nuclear Fusion

The atomic mass of Uranium `""_92^238"U"` is 238.0508 u, while that of Thorium `""_90^234"Th"` is 234.0436u, and that of Helium `""_2^4"He"` "is 4.0026u. Alpha decay converts `""_92^238"U"` into `""_92^234"Th"` as, shown below:

`""_92^238"U" -> ( ""_90^234"Th" + ""_2^4"He" + "Energy" )`

Appears in 1 question paper
Chapter: [13] Nuclei
Concept: Atomic Masses and Composition of Nucleus

What is a neutrino?

Appears in 1 question paper
Chapter: [13] Nuclei
Concept: Atomic Masses and Composition of Nucleus

Read the passage given below and answer the questions that follow.

Mr. Ravi had been living in a small town with his family for many years. He decided to shift to a city when he learnt that a nuclear power plant would be built in his town. His son Prakash, who was a science teacher, did not agree with his father’s decision.

Prakash explained to his father how mass defects during nuclear fission released energy. He assured his father that the authorities were taking all the possible safety measures to avoid any kind of nuclear mishap. Mr. Ravi understood the scientific explanation given by his son and decided not to shift to another place.

  1. What is the cause of energy generation of a nuclear reactor during nuclear fission?
  2. Write one nuclear reaction for nuclear fission that takes place in a nuclear reactor.
  3. Give the formula for the energy generation that takes place in the nuclear reactor.
Appears in 1 question paper
Chapter: [13] Nuclei
Concept: Nuclear Reactions

What conclusion is drawn from Rutherford’s scattering experiment of α-particles?

Appears in 1 question paper
Chapter: [13] Nuclei
Concept: Atomic Masses and Composition of Nucleus

Name the type of nuclear reaction that takes place in the core of the Sun.

Appears in 1 question paper
Chapter: [13] Nuclei
Concept: Nuclear Reactions

In a nuclear reactor, state the use of graphite rods.

Appears in 1 question paper
Chapter: [13] Nuclei
Concept: Nuclear Reactions

In a nuclear reactor, state the use of cadmium rods.

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Chapter: [13] Nuclei
Concept: Nuclear Reactions

Calculate the energy released in the following nuclear fusion reaction:

\[\ce{^2_1H + ^2_1H -> ^4_2He + energy}\]

Mass of \[\ce{^2_1H = 2.014102 u}\]

Mass of \[\ce{^4_2He = 4.002604 u}\]

Appears in 1 question paper
Chapter: [13] Nuclei
Concept: Nuclear Reactions

Find the energy released during the following fission reaction.

\[\ce{_92^235U + _0^1n-> _92^236U->_36^90Kr + _56^143Ba + 3 _0^1n}\]

  Mass(u)
235U 235.0439
90Kr 89.9195
143Ba 142.9206
1n 1.0087
Appears in 1 question paper
Chapter: [13] Nuclei
Concept: Nuclear Reactions
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