Please select a subject first
Advertisements
Advertisements
State Bohr's postulate to explain stable orbits in a hydrogen atom. Prove that the speed with which the electron revolves in nth orbit is proportional to `(1/"n")`.
Concept: Bohr’s Model for Hydrogen Atom
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
Consider the fission of `""_92^238"U"` by fast neutrons. In one fission event, no neutrons are emitted and the final end products, after the beta decay of the primary fragments, are `""_58^140"Ce"` and `""_44^99"Ru"`. Calculate Q for this fission process. The relevant atomic and particle masses are
`"m"(""_92^238"U")` = 238.05079 u
`"m"(""_58^140"Ce")` = 139.90543 u
`"m"(""_44^99"Ru")` = 98.90594 u
Concept: Mass-energy and Nuclear Binding Energy >> Nuclear Binding Energy
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 and Nuclear Binding Energy >> Mass - Energy
Write the basic nuclear process underlying β+ and β– decays.
Concept: Radioactivity >> Beta Decay
Define the terms (i) half-life (T1/2) and (ii) average life (τ). Find out their relationships with the decay constant (λ).
Concept: Mass-energy and Nuclear Binding Energy >> Nuclear Binding 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 and Nuclear Binding Energy >> Mass - Energy
Write the relationship between the size of a nucleus and its mass number (A)?
Concept: Mass-energy and Nuclear Binding Energy >> Mass - Energy
In a given sample, two radioisotopes, A and B, are initially present in the ration of 1 : 4. The half lives of A and B are respectively 100 years and 50 years. Find the time after which the amounts of A and B become equal.
Concept: Law of Radioactive Decay
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
Explain the release of energy in nuclear fission and fusion on the basis of binding energy per nucleon curve.
Concept: Mass-energy and Nuclear Binding Energy >> Nuclear Binding Energy
How mass defect is related to the stability of the nucleus?
Concept: Atomic Mass, Mass - Energy Relation and Mass Defect
With the help of a neat circuit diagram, explain the working of a photodiode.
Concept: Special Purpose P-n Junction Diodes
Meeta's father was driving her to school. At the traffic signal, she noticed that each traffic light was made of many tiny lights instead of a single bulb. When Meeta asked this question to her father, he explained the reason for this.
Answer the following questions based on above information:
(i) What were the values displayed by Meeta and her father?
(ii) What answer did Meeta's father give?
(iii) What are the tiny lights in traffic signals called and how do these operate?
Concept: Special Purpose P-n Junction Diodes
