The impurity atoms which are mixed with pure silicon to make a P-type semiconductor are those of
|
(a) Phosphorus |
(b) Boron |
(c) Antimony |
(d) Copper |
(b) Boron
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A wire carrying a current i is placed in a uniform magnetic field in the form of the curve y = asin
0 ≤ x ≤ 2L. The force acting on the wire is
|
(a) |
(b) iBL |
(c) 2iBL |
(d) Zero |
The attenuation in optical fibre is mainly due to
|
(a) Absorption |
(b) Scattering |
|
(c) Neither absorption nor scattering |
(d) Both (a) and (b) |
Assertion : The electrical conductivity of earth's atmosphere decreases with altitude.
Reason : The high energy particles (i.e. 𝛾-rays and cosmic rays) coming from outer space and entering our earth's atmosphere cause ionisation of the atoms of the gases present there and the pressure of gases decreases with increase in altitude.
|
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
|
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
|
(c) If assertion is true but reason is false. |
|
(d) If assertion is false but reason is true. |
In Young’s double slit experiment, distance between two sources is 0.1 mm. The distance of screen from the sources is 20 cm. Wavelength of light used is 5460 Å. Then angular position of the first dark fringe is
|
(a) 0.08° |
(b) 0.16° |
(c) 0.20° |
(d) 0.313° |
A charge of 
is placed on each of the 64 identical drops of radius 2cm. They are then combined to form a bigger drop. Find its potential
|
(a) 7.2 |
(b) 7.2 |
(c) 1.44 |
(d) 1.44 |
Absorption of X-ray is maximum in which of the following different sheets
|
(a) Copper |
(b) Gold |
(c) Beryllium |
(d) Lead |
