A convex lens made of glass has focal length 0.15 m in air. Ifthe refractive index of glass is $\frac{3}{2}$ and that of water is $\frac{4}{3}$, the focal length of lens when immersed in water is

• 0.45 m

• 0.15 m

• 0.30 m

• 0.6 m 

In a common emitter amplifier the input signal is applied across

• anywhere

• emitter-collector

• collector-base

• base-emitter

In a radioactive disintegration, the ratio of initial number of atoms to the number of atoms present at an instant of time equal to its mean life is

• $\frac{1}{{\mathrm{e}}^2}$

• $\frac{1}{\mathrm{e}}$

• e

• e²

A ray oflight is incident on a surface of glass slab at an angle 45°. If the lateral shift produced per unit thickness is $\frac{1}{\sqrt{3}}$ m, the angle of refraction produced is

• ${\tan }^{-1} \left(\frac{\sqrt{3}}{2}\right)$

• ${\tan }^{-1} \left(1 - \sqrt{\frac{2}{3}}\right)$

• ${\sin }^{-1} \left(1 - \sqrt{\frac{2}{3}}\right)$

• ${\tan }^{-1} \left(\sqrt{\frac{2}{\sqrt{3} - 1}}\right)$

For the constructive interference the path difference between the two interfering waves must be equal to

• (2n + 1) λ

• 2nπ

• nλ

• $\left(2\mathrm{n} + 1\right) \frac{\mathrm{\lambda }}{2}$

46.

The kinetic energy of an electron gets tripled, then the,de-Broglie wavelength associated with it changes by a factor

• $\frac{1}{3}$

• $\sqrt{3}$

• $\frac{1}{\sqrt{3}}$

• 3

The amount of energy released when one microgram of matter is annihilated is

• 25 kWh

• 9 × 10¹⁰ kWh

• 3 × 10¹⁰ kWh

• 0.5 × 10⁵ kWh

β- decay means emission of electron from

• innermost electron orbit

• a stable nucleus

• outermost electron orbit

• radioactive nucleus

G P Thomson experimentally confirmed the existence of matter waves by the phenomena

• diffraction

• refraction

• polarisation

• scattering

Two luminous point sources separated by a certain distance are at 10 km from an observer. If the aperture of his eye is 2.5 × 10^-3 m and the wavelength of light used is 500 nm, the distance of separation between the point sources just seen to be resolved is

• 12.2 m

• 24.2 m

• 2.44 m

• 1.22 m