Explanation:
The concept of holes was introduced so as to occupy the empty spaces left by the missing electron. For example, in a valence band, when an electron jumps from valence to conduction band, an empty space is created in valence band which is occupied by a hole.
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The unit of mutual conductance of a triode valve is
|
(a) Siemen |
(b) Ohm |
(c) Ohm metre |
(d) Joule Coulomb–1 |
The tail of the comet is due to
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(a) Vaporisation of water on the comet |
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(b) Sublimation of vapour in the comet |
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(c) Cooling of water in the comet |
|
(d) Vaporisation of heat in the comet |
In an apparatus, the electric field was found to oscillate with an amplitude of 18 V/m. The magnitude of the oscillating magnetic field will be
|
(a) 4 |
(b) 6 |
(c) 9 |
(d) 11 |
An achromatic combination of lenses produces
|
(a) Coloured images |
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(b) Highly enlarged image |
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(c) Images in black and white |
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(d) Images unaffected by variation of refractive index with wavelength |
A man is 180 cm tall and his eyes are 10 cm below the top of his head. In order to see his entire height right from toe to head, he uses a plane mirror kept at a distance of 1m from him. The minimum length of the plane mirror required is
| (a) 180 cm | (b) 90 cm | (c) 85 cm | (d) 170 cm |
A radioactive sample has 
active atoms at t = 0. If the rate of disintegration at any time is R and the number of atoms is N, then the ratio R/N varies with time as
|
(a)
|
(b)
|
(c)
|
(d)
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