In communication system, a repeater is used to extend the range to transmission. It is the combination of

Two wires of different materials have same length $$L$$ and same diameter $$d$$. The second wire is connected at the end of the first wire and forms one single wire of double the length. This wire is subjected to stretching force $$F$$ to produce the elongation I. The two wires have

When wavelength of light used in optical instruments A and B are 4500$$\mathop A\limits^o $$ and 6000$$\mathop A\limits^o $$ respectively, the ratio of resolving power of A to B will be

The light of wavelength $$\lambda$$ incident on the surface of metal having work function $$\phi$$ emits the electrons. The maximum velocity of electrons emitted is [ $$c=$$ velocity of light, $$h=$$ Planck's constant, $$m=$$ mass of electron]