UNIT-I

Tutorials

1. The work function for Cadmium is 4.08 eV, what must be the wavelength of radiation incident on Cadmium, so that maximum velocity of photo-electrons will be 7.2 x 105 m/s?

2. The de-Broglie wavelength associated with an electron is 0.1 Å. Find the potential difference by which the electron is accelerated.

3. Calculate the energy difference between the ground state and the first excited state for an electron in a box of length 1 Å.

UNIT-II

1.  A semiconductor has a band gap of 1.5 eV. What is the minimum wavelength in nm required to promote an electron from the valence to the conduction band?

2.  A semiconductor has a wavelength of 1.55 μm. Find its band gap in eV.

UNIT- III

1. A pure semiconductor has charge concentration 5 x 1019 carriers/m3 at room temperature. Find the conductivity and resistivity of the semiconductor. The mobilities of electron and holes are 0.4 and 0.2 m2/V-s respectively.

2. Calculate the intrinsic carrier concentration and conductivity at 300 K in germanium having energy gap 0.72 eV. Mobilities of electrons and holes are 0.4 and 0.2 m2/V-s respectively.  [m*e=m*h=m0].

3. Calculate the intrinsic concentration of charge carriers of Germanium at 300K. Eg for Germanium is 0.67 eV.  [m*e=0.12mo & m*h=0.28mo, where mo=9.1×10-31Kg]

4. In a Hall coefficient experiment, a current of 0.25A is sent through a metal strip having thickness of 0.2 mm and width 5 mm. The Hall voltage is found to be 0.15 mV when a magnetic field of 2000 Gauss is used. What is the carrier concentration?

5. The RH of a specimen is 3.66 x 10-4 m3/C. its resistivity is 8.93 x10-3Ωm. Find the carrier concentration(n) and mobility (µ).

6. A copper strip 2.0cm wide and 1.0mm thick is placed in a magnetic field with B=1.5 wb/m2. If a current of 200 A is set up in the strip, calculate Hall voltage that appears across the strip. Assume RH=6×10-7m3/C.

UNIT-IV

1. The numerical aperture of an optical fiber is 0.39. If the difference in the refractive indices of the material of its core and the cladding is 0.05, calculate the refractive index of material of the core.

2. Calculate the numerical aperture and acceptance angle for an optical fiber with core and cladding refractive indices being 1.48 and 1.45 respectively.

3. A signal of 100 mW is injected into a fiber. The out coming signal from the other end is 40 mW. What is the loss in dB?

4. Calculate the numerical aperture and acceptance angle for an optical fiber with core and cladding refractive indices being 1.50 and 1.48 respectively.

UNIT- V

1. Find the Relative permeability of a ferromagnetic material if a field of strength 220 amp/m produces a magnetization 3300 amp/m in it.

2. The magnetic field intensity in a piece of oxide is 106 amp/m. If the susceptibility of the materials is 1.5×10-3, calculate the magnetization of the material.