In an experiment of photoelectric emission, for incident light of 4000A0, stopping potential is 2V. If the wavelength of incident light is made 3000A0, then the stopping potential will be
Less than 2V
More than 2V
2V
zero
In a full wave rectifier output is taken across a load resistor of 800ohm.If the resistance of diode in forward biased condition is 200 ohm,the efficiency of reflection of rectification of ac power into dc power is
64.96%
40.6%
81.2%
50%
in a half wave rectifier output is taken across a 90 ohm load resistor. If the resistance of diode in forward biased condition is 10 ohm, the efficiency o rectification of ac power into dc power is
73.08%
36.54%
A photo-cathode is irradiated in turn by light of wavelengths 4000 A0 and 6200 A0 respectively. The ratio of the stopping potentials in the two cases is found to be 2:1. The work function of the photo-cathode is nearly
1.2 eV
0.9 eV
1.5 eV
0.6 eV
The elementary particles heavier than nucleons are called
mesons
neutrons
hyperons
Leptons
The energy released by fission from 2g of 23592U in KWH is.(The energy released per fission is 200MeV).
2.27x104
4.54x104
4.54x106
2.27x106
An explosion of atomic bomb releases an energy of 7.6x1013J.If 200 MeV energy is released on fission of one 235U atom the number of uranium atoms undergoing fission,and the mass of uranium used in the bomb is
1.756x1024,976.66g
1.756x1014,956.66g
2.375x1012,826.66g
2.375x1024,926.66g
An intrinsic semi conductor has 1018/m3 free electron and is doped with pentavalent impurity of 1024/m3.Then the free electrons density order increases by
4
3
5
6
When a monochromatic light of frequency v is incident on a metal, stopping potential is V0. Frequency of the incident light for which stopping potential becomes 2V0 is
V
v+(eV0/h)
2v+(eV0/h)
v-(eV0/h)
The wave length of the Kαline for an element of atomic number 43 is λ.Then the wavelength of the Kαline for an element of atomic number 29,is
(43/29) λ
(42/28) λ
(9/4) λ
(4/9) λ
An electron beam moving with a speed of 2x107ms-1 enters a magnetic field of induction 3x10-3T, directed perpendicular to its direction of motion. The intensity of electric field applied so that the electron beam is undeflected due to the magnetic field is
0.66x1010NC-1
12x104NC-1
1.5x104NC-1
6x104NC-1
7N14+2He4→X+1H1 then ‘X’ is
9F18
10Ne18
8O17
8C15
In Millikans oil drop experiment, an oil drop of radius r charge q falls under the gravity with a terminal velocity Vg and moves up with a terminal velocity Ve in the uniform vertical electric field of intensity E. If η is coefficient of viscosity of air, the charge of oil drop is
4πηr(Vg+Ve)/E
4πηr(Ve-Vg)/E
6πηr(Vg+Ve)/E
6πηr(Ve-Vg)/E
In a photoelectric cell, wavelength of the incident light is changed from 4000A0 to 3600A0. Change in stopping potential will be nearly
0.14V
0.24V
0.34V
0.44V
At least how many thermal neutrons should be available to start a fission reaction
2
1
The rate constant of the reaction at temperature 200K is 10 times than the rate constant at 400K.The activation energy of the reaction is
1842.4R
921.2R
460.6R
230.3R
In a p-n junction the depletion region is 400nm wide and electric field of 5x105Vm-1 exists in it. The minimum energy of a conduction electron, which can diffuse from n-side to the p-side is
4eV
5eV
0.4eV
0.2eV
Percentage of mass lost during the fission of 42U235 approximately is
0.01%
0.1%
0.7%
0.9%
200MeV energy is released when one nucleus of 235U undergoes fission. The number of fissions per second required for producing a power of 1 megawatt
3.125x1012
3.125x1016
3.125x108
3.125x1010