Which is the wrong statement in following sentences? A device in which P and N-type semiconductors are used is more useful then a vacuum type because
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(a) Power is not necessary to heat the filament |
|
(b) It is more stable |
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(c) Very less heat is produced in it |
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(d) Its efficiency is high due to a high voltage across the junction |
(d) Its efficiency is high due to a high voltage across the junction
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The addition of antimony atoms to a sample of intrinsic germanium transforms it to a material which is
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(a) Superconductor |
(b) An insulator |
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(c) N-type semiconductor |
(d) P-type semiconductor |
Huygen's conception of secondary waves
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(a) Allow us to find the focal length of a thick lens |
|
(b) Is a geometrical method to find a wavefront |
|
(c) Is used to determine the velocity of light |
|
(d) Is used to explain polarisation |
The mass defect per nucleon is called
|
(a) Binding energy |
(b) Packing fraction |
(c) Ionisation energy |
(d) Excitation energy |
Monochromatic green light of wavelength 5 
illuminates a pair of slits 1 mm apart. The separation of bright lines on the interference pattern formed on a screen 2 m away is
|
(a) 0.25 mm |
(b) 0.1 mm |
(c) 1.0 mm |
(d) 0.01 mm |
A plano convex lens is made of glass of refractive index 1.5. The radius of curvature of its convex surface is R. Its focal length is
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(a) R/ 2 |
(b) R |
(c) 2R |
(d) 1.5 R |
In a working nuclear reactor, Cadmium rods, (control rods) are used to
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(a) Speed up neutrons |
(b) Slow down neutrons |
|
(c) Absorb some neutrons |
(d) Absorb all neutrons |
When the current flowing in a circular coil is doubled and the number of turns of the coil in it is halved, the magnetic field at its centre will become
|
(a) Four times |
(b) Same |
(c) Half |
(d) Double |