Electronics — Physics STD 12 Science — Question

Decay constant of radium is λ. By a suitable process its compound radium bromide is obtained. The decay constant of radium bromide will be(a) λ(b) More than  λ(c) Less than λ (d) Zero

Light of two different frequencies whose photons have energies 1eV and 2.5eV respectively, successively illuminates a metal of work function 0.5eV. The ratio of maximum kinetic energy of the emitted electron will be(a) 1 : 5(b) 1 : 4(c) 1 : 2(d) 1 : 1

Select the correct statement(a) In a full wave rectifier, two diodes work alternately (b) In a full wave rectifier, two diodes work simultaneously(c) The efficiency of full wave and half wave rectifiers is same(d) The full wave rectifier is bi-directional

If ‘p’ region of a semi conductor is connected to negative and ‘n’ region to positive pole, it is said to be:

Kilowatt hour is the unit of :

Which of the following figures correctly shows the phase relation between the input signal and the output signal of triode amplifier.

At what distance from a convex lens of focal length 30 cm, an object should be placed so that the size of the image be 1/2 of the object(a) 30 cm(b) 60 cm(c) 15 cm(d) 90 cm

Two sources of waves are called coherent if(a) Both have the same amplitude of vibrations(b) Both produce waves of the same wavelength(c) Both produce waves of the same wavelength having constant phase difference(d) Both produce waves having the same velocity