Explanation:
The focal length of a lens is inversely proportional to the refractive index of the lens and the refractive index of the lens is inversely proportional to the square of wavelength. Therefore, the focal length is directly dependent on wavelength; it increases when the wavelength is increased.
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Two PN-junctions can be connected in series by three different methods as shown in the figure. If the potential difference in the junctions is the same, then the correct connections will be
|
(a) In the circuit (1) and (2) |
(b) In the circuit (2) and (3) |
| (c) In the circuit (1) and (3) | (d) Only in the circuit (1) |
In the grid circuit of a triode a signal E = 2
is applied. If m = 14 and rp =10 kW then root mean square current flowing through 
will be
|
(a) 1.27 mA |
(b) 10 mA |
(c) 1.5 mA |
(d) 12.4 mA |
Two resistors are connected (a) in series (b) in parallel. The equivalent resistance in the two cases are 9 ohm and 2 ohm respectively. Then the resistances of the component resistors are
|
(a) 2 ohm and 7 ohm |
(b) 3 ohm and 6 ohm |
(c) 3 ohm and 9 ohm |
(d) 5 ohm and 4 ohm |
A zone plate of focal length 60 cm, behaves as a convex lens, If wavelength of incident light is 6000
, then radius of first half period zone will be
|
(a) 36 |
(b) 6 |
(c) |
(d) 6 |
Three capacitors of 2μF, 3μF and 6μF are joined in series and the combination is charged by means of a 24 volt battery. The potential difference between the plates of the 6 μF capacitor is
|
(a) 4 volt |
(b) 6 volt |
(c) 8 volt |
(d) 10 volt |
The internal resistance of a cell of e.m.f. 12V is 5 
. It is connected across an unknown resistance. Voltage across the cell, when a current of 60 A is drawn from it, is
|
(a) 15 V |
(b) 12 V |
(c) 9 V |
(d) 6 V |
