Question

Tutorial 1:

1) Find the ratio of populations of the two states in a He-Ne LASER that produces light

of wavelength 6328 Å at 270C.

2) A gas LASER is generating a laser beam of 4 mW power. Calculate the number of

photons emitted by the laser. The wavelength of the emitted radiation is 680nm.

3) If the acceptance cone for a given fibre is .°. Calculate the maximum entrance

angle & numerical aperture. If the cladding glass has a refractive index of 1.52. Calculate

the refractive index of the core.

4) The numerical aperture of a fibre is . & relative refractive index is .. Determine

the indices of the core & cladding of a fibre.

5) Calculate natural frequency of 40mm length of pure iron. Given the density of pure

iron is .×/& Young’s modulus is ×/. Can you use it in

magnetostriction oscillator to produce ultrasonic wave?

6) An ultrasonic source of . sends down a pulse towards the seabed which

returns after . . The velocity of sound in sea water is /. Calculate the

depth of sea.

7) Calculate the thickness of quartz plate which is used to produce ultrasonic waves of

2MHz. Density of quartz is 2.65× kg/ & Young’s modulus is ×/.

8) Calculate the fundamental frequency of quartz crystal 1mm thick &density

/, =×/.

9) Certain piezoelectric crystal of thickness 4mm produces ultrasonic waves of frequency

400 kHz. Calculate the thickness of this crystal to produce ultrasonic frequency of 500

kHz.

10) Calculate the length of nickel rod required to produce frequency of 100 kHz. Density

of nickel is 8908 / & Young’s modules is .×/.​

Answer 1

Answer:

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