Photon of frequency $$v$$ has a momentum associated with it. If $$c$$ is the velocity of light, the momentum is

The half-life period of a ratio-active element $$X$$ is same as the mean life time of another ratio-active element $$Y.$$ Initially they have the same number of atoms. Then

Which of the following transitions in hydrogen atoms emit photons of highest frequency ?

Carbon, silicon and germanium have four valence electrons each. At room temperature which one of the following statements is most appropriate ?