The energy band gap is maximum in

Which of the following are not electromagnetic waves?

If two mirrors are kept at $${60^ \circ }$$ to each other, then the number of images formed by them is

A wire when connected to $$220$$ $$V$$ mains supply has power dissipation $${P_1}.$$ Now the wire is cut into two equal pieces which are connected in parallel to the same supply. Power dissipation in this case is $${P_2}.$$ Then $${P_2}:{P_1}$$ is