Avalanche breakdown in a p-n junction diode is due to
shift of fermi level
widening of forbidden gap
high impurity concentration
cummulative effect of conduction band electrons collision
If the radius of the first Bohr orbit of the hydrogen atom is 5.29 x 10' m, the radius of the second orbit will be
21.16 x 10−11 m
15.87 x 10−11 m
10.58 x 10−11 m
2.64 x 10−11 m
A.
21.16 x 10−11 m
Radius of Bohr orbit, r n2
r2 = 5.29 × 10−11 × 4
= 21.16 × 10−11 m
Number of nuclei of a radioactive substance at time t = O are 2000 and 1800 at time t = 2s. Number of nuclei left after t = 6s is
1442
1554
1652
1458
92U238 on absorbing a neutron goes over to 92U239. This nucleus emits an electron to go over to neptunium which on further emitting an electron goes over to plutonium. The resulting plutonium can be expressed as
94Pu239
90Pu219
93Pu240
92Pu240
The energy of a photon corresponding to the visible light of maximum wavelength is approximately
1 eV
1.6 eV
3.2 eV
7 eV
If the binding energy of the electron in a hydrogen atom is 13.6 eV, the energy required to remove the electron from the first excited state of Li2+ is
30.6 eV
13.6 eV
3.4 eV
122.4 eV
To demonstrate the phenomenon of interference we require two sources which emit radiations of
nearly the same frequency
the same frequency
different wavelengths
the same frequency and having a definite phase relationship
To get three images of a single object, one should have two plane mirrors at an angle of
60°
90°
120°
30°
Consider telecommunication through optical fibres. Which of the following statements is not true?
Optical fibres can be of graded refractive index
Optical fibres are subjected to electromagnetic interference from outside
Optical fibres have extremely low transmission loss
Optical fibres may have homogeneous core with a suitable cladding