A light source approaches the observer with velocity 0.8 c. The doppler shift for the light of wavelength 5500 Å is
|
(a) 4400 Å |
(b) 1833 Å |
(c) 3167 Å |
(d) 7333 Å |
(c) 3167 Å
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The amplification factor of a triode is 20 and trans-conductance is 3 milli mho and load resistance 3 
then the voltage gain is
|
(a) 16.36 |
(b) 28 |
(c) 78 |
(d) 108 |
The combination of ‘NAND’ gates shown here under (figure) are equivalent to
|
(a) An OR gate and an AND gate respectively |
|
(b) An AND gate and a NOT gate respectively |
|
(c) An AND gate and an OR gate respectively |
|
(d) An OR gate and a NOT gate respectively. |
Four charges are placed on corners of a square as shown in figure having side of 5cm. If Q is one microcoulomb, then electric field intensity at centre will be
|
(a) 1.02 |
(b) 2.04 |
|
(c) 2.04 |
(d) 1.02 |
A semiconductor X is made by doping a germanium crystal with arsenic (Z = 33). A second semiconductor Y is made by doping germanium with indium (Z = 49). The two are joined end to end and connected to a battery as shown. Which of the following statements is correct
|
(a) X is P-type, Y is N-type and the junction is forward biased |
|
(b) X is N-type, Y is P-type and the junction is forward biased |
|
(c) X is P-type, Y is N-type and the junction is reverse biased |
|
(d) X is N-type, Y is P-type and the junction is reverse biased |
If nearly 
coulomb liberate 1 gm equivalent of aluminium, then the amount of aluminium (equivalent weight 9) deposited through electrolysis in 20 minutes by a current of 50 amp will be
|
(a) 0.6 gm |
(b) 0.09 gm |
(c) 5.4 gm |
(d) 10.8 gm |
The resistance of a reverse biased P-N junction diode is about
|
(a) 1 ohm |
(b) |
(c) |
(d) |
In an X-rays tube, the intensity of the emitted X-rays beam is increased by
| (a) Increasing the filament current | (b) Decreasing the filament current |
|
(c) Increasing the target potential |
(d) Decreasing the target potential |
The number of wavelengths in the visible spectrum
|
(a) 4000 |
(b) 6000 |
(c) 2000 |
(d) Infinite |
