Explanation:
In insulators, the electrons are very tightly bound to the nucleus. At a room temperature, thermal energy is not enough to push electrons into conduction band. The energy band gap is very high. Thus the conduction band is empty and the valence band is filled with electrons.
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Plane polarised light is passed through a polaroid. On viewing through the polaroid we find that when the polariod is given one complete rotation about the direction of the light, one of the following is observed
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(a) The intensity of light gradually decreases to zero and remains at zero |
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(b) The intensity of light gradually increases to a maximum and remains at maximum |
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(c) There is no change in intensity |
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(d) The intensity of light is twice maximum and twice zero |
Starting with a sample of pure 
of it decays into Zn in 15 min. The corresponding half-life is
| (a) 5 min |
(b) 7  min
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(c) 10 min |
(d) 15 min |
In Young's double slit experiment, the slits are 0.5 mm apart and interference pattern is observed on a screen placed at a distance of 1.0 m from the plane containing the slits. If wavelength of the incident light is 6000 Å, then the separation between the third bright fringe and the central maxima is
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(a) 4.0 mm |
(b) 3.5 mm |
(c) 3.0 mm |
(d) 2.5 mm |
Two slits, 4 mm apart, are illuminated by light of wavelength 6000 Å. What will be the fringe width on a screen placed 2m from the slits
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(a) 0.12 mm |
(b) 0.3 mm |
(c) 3.0 mm |
(d) 4.0 mm |
In a forward biased PN-junction diode, the potential barrier in the depletion region is of the form …
(a)
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(b)
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(c)
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(d)
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