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A narrow beam of protons, each having 4.1 MeV energy is approaching a sheet of lead (Z = 82). Calculate:
- the speed of a proton in the beam, and
- the distance of its closest approach
Concept: Alpha-particle Scattering and Rutherford’s Nuclear Model of Atom
A hydrogen atom makes a transition from n = 5 to n = 1 orbit. The wavelength of photon emitted is λ. The wavelength of photon emitted when it makes a transition from n = 5 to n = 2 orbit is ______.
Concept: The Line Spectra of the Hydrogen Atom
Write the ionisation energy value for the hydrogen atom.
Concept: Bohr’s Model for Hydrogen Atom
How is the size of a nucleus found experimentally? Write the relation between the radius and mass number of a nucleus.
Concept: Alpha-particle Scattering and Rutherford’s Nuclear Model of Atom
A nucleus with mass number A = 240 and BE/A = 7.6 MeV breaks into two fragments, each of A = 120 with BE/A = 8.5 MeV. Calculate the released energy.
Concept: Atomic Masses and Composition of Nucleus
Calculate the energy in fusion reaction:
`""_1^2H+_1^2H->_2^3He+n`, where BE of `""_1^2H`23He=7.73MeV" data-mce-style="position: relative;">=2.2323He=7.73MeV MeV and of `""_2^3He=7.73 MeV`
Concept: Nuclear Fusion
Asha's mother read an article in the newspaper about a disaster that took place at Chernobyl. She could not understand much from the articles and asked a few questions from Asha regarding the article. Asha tried to answer her mother's questions based on what she learnt in Class XII Physics.
(a) What was the installation at Chernobyl where the disaster took place? What according to you, was the cause of this disaster?
(b) Explain the process of release of energy in the installation at Chernobyl.
(c) What according to you, were the values displayed by Asha and her mother?
Concept: Mass - Energy
In a typical nuclear reaction, e.g.
`"_1^2H+"_1^2H ->"_2^3He + n + 3.27 \text { MeV },`
although number of nucleons is conserved, yet energy is released. How? Explain.
Concept: Mass - Energy
Write the relationship between the size of a nucleus and its mass number (A)?
Concept: Mass - Energy
Distinguish between isotopes and isobars.
Concept: Atomic Masses and Composition of Nucleus
Two nuclei have different mass numbers A1 and A2. Are these nuclei necessarily the isotopes of the same element? Explain.
Concept: Atomic Masses and Composition of Nucleus
A heavy nucleus P of mass number 240 and binding energy of 7.6 MeV per nucleon splits into two nuclei Q and R of mass number 110 and 130 and binding energy per nucleon of 8.5 MeV and 8.4 MeV respectively. Calculate the energy released in fission.
Concept: Nuclear Fission
(i) Explain with the help of a diagram the formation of depletion region and barrier potential in a pn junction.
Concept: Semiconductor Diode
Why is a zener diode considered as a special purpose semiconductor diode?
Concept: Semiconductor Diode
Answer the following question.
Three photodiodes D1, D2, and D3 are made of semiconductors having band gaps of 2.5 eV, 2 eV, and 3 eV respectively. Which of them will not be able to detect light of wavelength 600 nm?
Concept: Classification of Metals, Conductors and Semiconductors
Answer the following question.
Why photodiodes are required to operate in reverse bias? Explain.
Concept: Semiconductor Diode
Explain the formation of the barrier potential in a p-n junction.
Concept: Semiconductor Diode
Pieces of copper and of silicon are initially at room temperature. Both are heated to temperature T. The conductivity of ______.
Concept: Extrinsic Semiconductor
Answer the following giving reasons:
A p-n junction diode is damaged by a strong current.
Concept: Semiconductor Diode
Answer the following giving reasons:
Impurities are added to intrinsic semiconductors.
Concept: Intrinsic Semiconductor
