Does light or waves have any kind of mass? Just like the previous question,  Even I have been studying Hawking's A Brief History Of Time and even I was thinking of Einstein's General Relativity. But I was unable to accept his view of GRAVITY. I have been working on a theory which needs that Gravity effects Light. And so my question is that, Is there any kind of mass for Light? as it was being effected by Gravity?    Excuse me if any mistakes were done.   Plzz answer me.
Does a photon exert a gravitational pull? I know a photon has zero rest mass, but it does have plenty of energy. Since energy and mass are equivalent does this mean that a photon (or more practically, a light beam) exerts a gravitational pull on other objects? If so, does it depend on the frequency of the photon?
What is the meaning of speed of light $c$ in $E=mc^2$? is the famous mass-energy equation of Albert Einstein. I know that it tells that mass can be converted to energy and vice versa. I know that $E$ is energy, $m$ is mass of a matter and $c$ is speed of light in vacuum.   What I didn't understood is how we will introduce speed of light?  Atom bomb is made using this principle which converts mass into energy; in that the mass is provided by uranium but where did speed of light comes into play? How can speed of light can be introduced in atom bomb?