Optionals IAS Mains Physics: Questions 293 - 298 of 307

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Question 293

Pulse Dispersion in Step Index and Parabolic Index Fibres

Appeared in Year: 2016

Describe in Detail

Essay▾

The refractive indices of core and cladding in a step-index optical fibre are 1.52 and 1.48 respectively. The diameter of the core is , Calculate the V parameter and the maximum number of modes supported by the fibre. (Marks: 10)

Explanation

Refractive index of core be

Refractive index of cladding be

Diameter of the fibre,

Wavelength of the light be

number is given by

=

=

=

=

The maximum number of modes supported by an fibre is given by

=

=

= modes

In cases of GRIN (Graded Index) fibres, for larger of

Question 294

Spectroscopic Notation of Atomic States
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Appeared in Year: 2016

Describe in Detail

Essay▾

Compute the allowed spectral terms for two non-equivalent P-electrons on the basis of Pauli՚s exclusion principle. (Marks: 10)

Explanation

Let us imagine the atom to be placed in a very strong magnetic field where all the internal couplings are broken down. The individual & vectors then process independently around the magnetic field with quantised components and respectively. The value of for a electron is and hence the values of are and ; while those of are .

Now, all possi…

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Question 295

Elementary Ideas About High Temperature Superconductivity

Appeared in Year: 2003

Write in Short

Short Answer▾

What are high superconductors? Give two examples indicating their transition temperatures. Differentiate between the conventional and high superconductors.

(Marks: 12)

Question 296

Appeared in Year: 2003

Describe in Detail

Essay▾

Define Fermi energy. For an ideal Fermi gas of Particles at absolute zero temperature, show that the total energy of the system is where is the Fermi energy. (Marks: 20)

Explanation

The Fermi energy is defined as the energy of the top most filled level in the ground state of the electron system. At absolute zero the chemical potential is equal to the Fermi energy, defined as the energy of the top most filled orbital at absolute zero. It is also the maximum kinetic energy an electron can attain at k. It is a constant for eac…

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Question 297

Spectroscopic Notation of Atomic States

Appeared in Year: 2000

Describe in Detail

Essay▾

Determine all the term symbols of equivalent electrons and arrange these states in increasing order of energy. Justify your answer. (Marks: 20)

Explanation

Let us imagine the atom to be placed in a very strong magnetic field where all the internal couplings are broken down. The individual and vectors then process independent around the magnetic field with quantised components and respectively. The value of for a p-electron is 1 and hence the values of are , while those of are and . Now, all po…

… (465 more words) …

Question 298

Appeared in Year: 2003

Describe in Detail

Essay▾

Number of non-interacting electrons are confined in a cube of volume . Obtain an expression for the Fermi energy. (Marks: 30)

Explanation

Let us consider the behaviour of the free gas in a three-dimensional metallic crystal. The potential of the electrons inside the crystal is constant and may be taken as zero, whereas it has a large value outside the crystal. For simplicity, the three-dimensional crystal may be regarded as a cubical box having length of edge equal to . The free par…

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