Q. The wavelength of light emitted by GaAs laser is 8670 x 10¯¹ᴼ m. If h = 6.626 x 10¯³⁴ Js, velocity of light = 3 x 10⁸ m/s and eV = 1.602 x 10¯¹⁹ J, the energy gap in GaAs is

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Q. Diamagnetic materials do not have permanent magnetic dipoles.

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Q. A piece of copper and another piece of Germanium are cooled from 30°C to 80 K. The resistance of

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Q. The dipole moment per unit volume P as a function of E for an insulator is

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Q. A good dielectric should have

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Q. Magnetic hysteresis phenomenon is explained by

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Q. The relation between thermal conductivity K (W/m/°C), heat flow density Q (watt/m²) and dT/dx (°C per metre) is

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Q. Assertion (A): The equation D = ∈₀∈ᵣE is applicable only to isotropic materials.

Reason (R): In polycrystalline materials, the directional effects are absent.

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Q. Assertion (A): For a dielectric, P = ∈₀(∈ᵣ - 1) E.

Reason (R): Dipole moment per unit volume is called polarization of dielectric.

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Q. Assertion (A): Ferrites are very useful at very high frequencies.

Reason (R): Ferrites have high permeability and high resistivity.

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Q. In a conductor the current flow is due to

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Q. When an electron moves at velocity v in combined electric and magnetic fields E and H, the Lorentz force F is F = - e(E + v x B).

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Q. When Schrodinger equation is applied to the motion of electron in the field of protons, the physically acceptable solutions for the wave function exist for quantum number which are

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Q. For dielectrics in alternating field, polarizability αe is a complex quantity. The imaginary part of ae is zero for

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Q. In the wave mechanical theory, the maximum of the charge distribution in the ground state occurs for a distance from the nucleus equal to

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Q. The induced magnetic dipole moment has a direction opposite to the applied magnetic field.

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Q. An atom of polarizability a is placed in a homogeneous electric field E. The energy stored in polarized atom is

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Q. If B, H and M denote flux density, field intensity and magnetisation, B = μ₀ (H + M).

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Q. A capacitor can be represented by a capacitance and resistance in parallel. For a good capacitor, this parallel resistance should be

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Q. Assertion (A): Ionic solids, in general, have no electrical conductivity.

Reason (R): In ionic solids, electrons are tightly bound to the nucleus.

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