MCQ
After losing two electrons, an atom of Helium becomes equivalent to:
- A$\alpha$ -particle
- B$\beta$ -particle
- C$\gamma$ -particle
- DDeuterium nucleus
Explanation:
$^4_2$He→$^4_2$He+2+2e−
$^4_2$He+2 is alpha particle. Because it has charge equal to +2e and mass is four times the mass of one proton.
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Photo-electric effect can be explained by
|
(a) Corpusular theory of light |
(b) Wave nature of light |
|
(c) Bohr’s theory |
(d) Quantum theory of light |
The alloys constantan and manganin are used to make standard resistance due to they have
|
(a) Low resistivity |
(b) High resistivity |
|
(c) Low temperature coefficient of resistance |
(d) Both (b) and (c) |
A convex lens of focal length 84 cm is in contact with a concave lens of focal length 12 cm. The power of combination (in diopters) is
|
(a) 25/24 |
(b) 25/18 |
(c) – 50/7 |
(d) + 50/7 |
A and B are two radioactive substances whose half lives are 1 and 2 years respectively. Initially 10 gm of A and 1 gm of B is taken. The time (approximate) after which they will have same quantity remaining is
|
(a) 6.62 years |
(b) 5 years |
(c) 3.2 years |
(d) 7 years |
In a nuclear fission reaction
|
(a) Two light nuclei combine to produce a heavier nucleus |
|
(b) A light nucleus bombarded by thermal neutrons breaks up |
|
(c) A heavy nucleus bombarded by thermal neutrons breaks up |
|
(d) A heavy nucleus breaks up by itself |
The magnetic compass is not useful for navigation near the magnetic poles because
|
(a) The magnetic field near the poles is zero |
|
(b) The magnetic field near the poles is almost vertical |
|
(c) At low temperature, the compass needle looses its magnetic properties |
|
(d) Neither of the above |
In good conductors of electricity, the type of bonding that exists is
|
(a) Ionic |
(b) Vander Waals |
(c) Covalent |
(d) Metallic |
If a diamagnetic substance is brought near north or south pole of a bar magnet, it is
| (a) Attracted by the poles |
| (b) Repelled by the poles |
|
(c) Repelled by the north pole and attracted by the south pole |
|
(d) Attracted by the north pole and repelled by the south pole |