A p-n photodiode is made of a material with a band gap of 2.0 eV. The minimum frequency of the radiation that can be absorbed by the material is nearly
10 x 1014 Hz
5 x 1014 Hz
1 x 1014 Hz
1 x 1014 Hz
Two radioactive materials X1 and X2 have decay constant 5 λ respectively. If initially, they have the same number of nuclei, then the ratio of the number of nuclei of X1 to that of X2 will be 1/e after a time
λ
λ/2
1/4λ
1/4λ
Two thin lenses of focal lengths f1 and f2 are in contact and coaxial. The power of the combination is
D.
If two thin lenses of focal lengths f1, f2 are placed in contact coaxially, then equivalent focal length of combination is
A particle of mass 1 mg has the same wavelength as an electron moving with a velocity of 3 x 106 ms-1. The velocity of the particle is.
(mass of electron = 9.1 x 10-31 kg)
2.7 x 10-18 ms-1
9 x 10-2 ms-1
3 x 10-31 ms-1
3 x 10-31 ms-1
If M (A, Z), MP and Mn denote the masses of the nucleus proton and neutron respectively in units of u (1 u = 931.5 MeV/c2) and BE represents its binding energy in MeV, then
M (A,Z) = ZMp + (A-Z)Mn - BE/c2
M (A,Z) = ZMp + (A-Z)Mn + BE
M (A,Z) = ZMp + (A-Z)Mn - BF
M (A,Z) = ZMp + (A-Z)Mn - BF
Two periodic waves of intensities I2 and I2 pass through a region at the same time in the same direction. The sum of the maximum and minimum intensities is
I1 + I2
A boy is trying to start a fire by focusing sunlight on a piece of paper using an equal convex lens of focal length 10 cm. The diameter of the sun is 1.39 x 109 m and its mean distance from the earth is 1.5 x 1011 m. What is the diameter of the sun's image on the paper?
9.2 x 10-4 m
6.5 x 10-4 m
6.5 x 10-5 m
6.5 x 10-5 m
Two points are located at a distance of 10 m and 15 m from the source of oscillation. The period of oscillation is 0.05 s and the velocity of the wave is 300 m/s. What is the phase difference between the oscillation of two points?
π/3
2π/3
π
π
Two nuclei have their mass number in the ratio of 1:3. The ratio of their nuclear densities would be
1:3
3:1
(3)1/3 : 1
(3)1/3 : 1