A silicon speciman is made into a P-type semi-conductor by dopping, on an average, one Indium atom per 5 
silicon atoms. If the number density of atoms in the silicon specimen is 5 
then the number of acceptor atoms in silicon per cubic centimetre will be
|
(a) 2.5 |
(b) 1.0 |
|
(c) 1.0 |
(d) 2.5 |
(c) 1.0 
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When the light source is kept 20 cm away from a photo cell, stopping potential 0.6 V is obtained. When source is kept 40 cm away, the stopping potential will be
|
(a) 0.3 V |
(b) 0.6 V |
(c) 1.2 V |
(d) 2.4 V |
Maximum useable frequency (MUF) in F-region layer is x, when the critical frequency is 60 MHz and the angle of incidence is 70°. Then x is
|
(a) 150 MHz |
(b) 170 MHz |
(c) 175 MHz |
(d) 190 MHz |
In the uranium radioactive series, the initial nucleus is 
and the final nucleus is 
. When the uranium nucleus decays to lead, the number of α - particles emitted will be
|
(a) 1 |
(b) 2 |
(c) 4 |
(d) 8 |
The potential difference between the cathode and the target in a Collidge tube is 100 kV. The minimum wavelength of the X-rays emitted by the tube is
|
(a) 0.66 Å |
(b) 9.38 Å |
(c) 0.246 Å |
(d) 0.123 Å |
