Explanation:
$\text{K}=\frac{1}{4\pi\in_\circ\text{k}}$ and its units is N−m2/ C2
It depend on system of unit and dielectric constant (k), that's medium between charges
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Half life of 
is 5 days. If we start with 50,000 atoms of this isotope, the number of atoms left over after 10 days is
|
(a) 5,000 |
(b) 25,000 |
(c) 12,500 |
(d) 20,000 |
Consider an optical communication system operating at l~ 800 nm. Suppose, only 1% of the optical source frequency is the available channel bandwidth for optical communication. How many channels can be accommodated for transmitting audio signals requiring a bandwidth of 8 kHz
|
(a) 4.8 × 108 |
(b) 48 |
(c) 6.2 × 108 |
(d) 4.8 × 105 |
Specific rotation of sugar solution is 0.01 SI units. 200 
of impure sugar solution is taken in a polarimeter tube of length 0.25m and an optical rotation of 0.4rad is observed. The percentage of purity of sugar is the sample is
|
(a) 80% |
(b) 89% |
(c) 11% |
(d) 20% |
A coil carrying electric current is placed in uniform magnetic field, then
|
(a) Torque is formed |
(b) E.M.f. is induced |
|
(c) Both (a) and (b) are correct |
(d) None of these |
Two light sources are said to be coherent if they are obtained from
|
(a) Two independent point sources emitting light of the same wavelength |
|
(b) A single point source |
|
(c) A wide source |
|
(d) Two ordinary bulbs emitting light of different wavelengths |
Coating of strontium oxide on Tungsten cathode in a valve is good for thermionic emission because
|
(a) Work function decreases |
|
(b) Work function increases |
|
(c) Conductivity of cathode increases |
|
(d) Cathode can be heated to high temperature |