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00000PH100121804

square well of width 2.5x 10m. Calculate the three lowest permissible
quantum energies of the electron.
Write three postulates of FD statistics and it's distribution equation.

Calculate the reverberation time of a hall having volume 4000 ന്‌ and total
sound absorption of 160 Sabine. Find the additional sound absorption required
for an optimum reverberation of 1.5 s.
An ultrasonic source of frequency 0.09 MHz sends down a pulse towards sea
bed which returns after 0.55 s. The velocity of sound in water is 1800 m/s.
Calculate the depth of the sea and wavelength of the pulse.
What is population inversion? Using energy level diagrams explain how it is
achieved in a Helium-Neon laser?
What are the advantages of optical fibre communication over conventional
mode of communication?
PART C

Answer any three questions, each carries 6 marks.
Write the differential equation of a forced harmonic oscillator. Derive the
expressions for the amplitude and phase difference.
Discuss in detail Fraunhofer diffraction at a single slit and obtain the
expression for width of central maximum.
Define circularly and elliptically polarised light. What is a quarter wave plate?
How it can be used to analyze circularly and elliptically polarized light?
Assuming the time dependent Schrodinger equation derive time independent
Schrodinger equation.
What are eigen values and eigen functions?

PART D

Answer any three questions, each carries 6 marks.
Define reverberation and reverberation time. Write Sabine’s formula. What is
its significance?
What is the principle of a piezoelectric oscillator? With the circuit diagram
explain the working of a piezoelectric oscillator.
Explain the construction and reconstruction of a hologram. Give its advantages
over photograph.
Define numerical aperture of an optic fibre. Obtain an expression for the
numerical aperture of a step index fibre.

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