Taking the earth to be a spherical conductor of diameter 12.8×103 km. Its capacity will be
711 μF
611 μF
811 μF
511 μF
The half-life of a radioactive substance is 3.6 days. How much of 20 mg of this radioactive substance will remain after 36 days?
0.0019 mg
1.019 mg
1.109 mg
0.019 mg
The kinetic energy of an electron is 5eV. Calculate the de-Broglie wavelength associated with it (h=6.6×10-34 Js, me =9.1×10-31 kg)
5.47Ao
10.9Ao
2.7Ao
None of these
The energy in MeV is released due to transformation of 1kg mass completely into energy is (c=3×108 m/s)
7.625×10MeV
10.5×1029MeV
2.8×10-28MeV
5.625×1029MeV
20 kV potential is applied across X-ray tube, the minimum wavelength of X-ray emitted will be
0.62 Ao
0.37 Ao
1.62 Ao
1.31 Ao
A.
0.62 Ao
(i)The minimum energy required to eject an electron from the surface is
called the photoelectric work function of the metal.
(ii)Energy greater than the work function of the metal (Φo)
required for electron emission from the metal surface can be supplied by suitably heating
(or) applying strong electric field or irradiating it by suitable frequency.
In the CB mode of a transistor, when the collector voltage is changed by 0.5 volt, the collector current changes by 0.05 mA. The output resistance will be
10 kΩ
20 kΩ
5 kΩ
2.5 kΩ
A student can distinctly see the object upto a distance 15 cm. He wants to see the blackboard at a distance of 3m. Focal length and power of lens used respectively will be
-4.8cm, -3.3D
-5.8cm, -4.3D
-7.5cm, -6.3D
-15.8cm, -6.33D
A thin glass prism (μ =15) in the position of minimum deviation deviates the monochromatic light ray by 10o, the refracting angle of prism is
20o
10o
30o
45o
Two thin lenses of powers 12 D and-2D respectively are placed in contact, the power, focal length and nature
respectively will be
8D, 0.8m, convex
14D, 0.5m, convex
5D, 0.2m, convex
10D, 0.1m, convex