If the work functions of three photosensitive materials are 1 eV, 2 eV and 3 eV respectively, then the ratio of the respective frequencies of light that produce photoelectrons of maximum kinetic energy of 1 eV from each of them is
1 : 2 : 3
2 : 3 : 4
1 : 1 : 1
3 : 2 : 1
During β− emission,
a neutron in the nucleus decays emitting an electron
an atomic electron is ejected
an electron already present within the nucleus is ejected
a part of the binding energy of the nucleus is converted into an electron
The binding energy per nucleon of 16O is 7.97 MeV and that of 17O is 7.75 MeV. The energy in MeV required to remove a neutron from 17O is
3.52
3.64
4.23
7.86
C.
4.23
BE per nucleon 16O = 7.97 MeV
BE per nucleon 17O = 7.75 MeV
17O → 0n1 + 16O
Energy required to remove neutron
= 17 × 7.75 − 16 × 7.97
= 4.23 MeV
If the ratio of the radius of a nucleus with 61 neutrons to that of helium nucleus is 3, then the atomic number of this nucleus is
27
47
51
61
The electron density of intrinsic semiconductor at room temperature is 1016 m-3. When doped with a trivalent impurity, the electron density is decreased to 1014 m- at the same temperature. The majority carrier density is
1016 m-3
1018 m-3
1021 m-3
1020 m-3
In a Zener diode regulated power supply, unregulated DC input of 10 V is applied. If the resistance (Rs) connected in series with a Zener diode is 200 Ω and the Zener voltage Vz =5V, the current across the resistance Rs is
15 mA
10 mA
25 mA
5 mA
To detect light of wavelength 500 nm, the photodiode must be fabricated from a semiconductor of minimum bandwidth of
1.24 eV
0.62 eV
2.48 eV
3.2 eV
If the height of TV tower is increased by 21%, then the transmission range is enhanced by
10 %
5 %
15 %
25 %
The range of a communication system can be extended by a
modulator
transmitter
repeater
receiver