Earth's magnetic field always has a horizontal component except at or Horizontal component of earth's magnetic field remains zero at
| (a) Equator | (b) Magnetic poles | (c) A latitude of 60o | (d) An altitude of 60o |
Earth's magnetic field always has a horizontal component except at or Horizontal component of earth's magnetic field remains zero at
| (a) Equator | (b) Magnetic poles | (c) A latitude of 60o | (d) An altitude of 60o |
(b) Magnetic poles
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There are
photons of frequency
in a beam of light. In an equally energetic beam, there are
photons of frequency
. Then the correct relation is
|
(a) |
(b) |
(c) |
(d) |

Correct exposure for a photographic print is 10 seconds at a distance of one metre from a point source of 20 candela. For an equal fogging of the print placed at a distance of 2 m from a 16 candela source, the necessary time for exposure is
|
(a) 100 sec |
(b) 25 sec |
(c) 50 sec |
(d) 75 sec |
If an electron enters a magnetic field with its velocity pointing in the same direction as the magnetic field, then
|
(a) The electron will turn to its right |
|
(b) The electron will turn to its left |
|
(c) The velocity of the electron will increase |
|
(d) The velocity of the electron will remain unchanged |
The decay constant λ of the radioactive sample is the probability of decay of an atom in unit time, then
|
(a) λ decreases as atoms become older |
|
(b) λ increases as the age of atoms increases |
|
(c) λ is independent of the age |
|
(d) Behaviour of λ with time depends on the nature of the activity |