A piece of copper and another of germanium are cooled from room temperature to $$77K,$$ the resistance of

The angle of incidence at which reflected light is totally polarized for reflection from air to glass (refractive index $$n$$) is :

When $$p$$-$$n$$ junction diode is forward biased then

A current $$i$$ ampere flows along an infinitely long straight thin walled tube, then the magnetic induction at any point inside the tube is