Optionals IAS Mains Physics: Questions 73 - 78 of 306

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Question 73

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Appeared in Year: 2000

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Essay▾

Derive an expression for the mass-energy equivalence using the principle of special relativity. (20 Marks)

Explanation

  • As we recall from elementary physics, the work W done on an object by a constant force of magnitude F that acts through the distance s, where F is in the same direction as s, is given by If no other forces on the object and the object starts from rest, all the work done on it becomes kinetic energy . In the general case where F need not be a const

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Question 74

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Appeared in Year: 2010

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Essay▾

If a photon of frequency collides with an electron of mass at rest, it well be scattered at some angle with a new frequency. Show that the change in wavelength is related to the scattering angle by the formula

Where is known as the Compton wavelength. (20 Marks)

Explanation

  • Compton treated the X-ray beam as a beam of photons, each of energy and linear momentum individually colliding with the electrons of foil. Let as consider a photon of energy and linear momentum incident along x-axis on an electron at rest in the laboratory coordinate system. After the collision, the photon shall be scattered in one direction an

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Question 75

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Appeared in Year: 2009

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Essay▾

List the characteristics of an ideal op-amp. Write the expression for the output voltage in terms of input voltages and resist tance values.

Figure of the ideal op-amp

Figure of the Ideal Op-Amp

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(20 Marks)

Explanation

The ideal op-amp has these characteristics: -

(i) Input impedance (differential or common mode) = infinity and so zero input current.

(ii) Output impedance (open loop) =0

(iii) Voltage gain = infinity

(iv) Common mode voltage gain = 0

(v) When both input are at same voltage (zero “offset voltage)

(vi) Output can change instantaneously (infinite slow ra

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Question 76

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Short Answer▾

Show that the circuit shown below is an exclusive OR gate.

Figure shows the OR gate

Figure Shows the or Gate

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(10 Marks)

Question 77

Principles of Fibre Optics Attenuation
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Appeared in Year: 2010

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Short Answer▾

What should be the refractive index of cladding of an optical fibre with numerical aperture with refractive index of core as? (10 Marks)

Question 78

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Appeared in Year: 2000

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Essay▾

What are the salient features of ferromagnetic? Explain how the curie law of paramagnetism is modified to Curie-Weiss law? (20 Marks)

Explanation

  • Like paramagnetism, ferromagnetism is also associated with the presence of permanent magnetic dipoles, but unlike paramagnetism, the magnetic moments of adjacent atoms in this case are aligned in a particular direction even in the absence of the applied magnetic field. Thus a ferromagnetic material exhibits a magnetic moment in the absence of a mag

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