Statement-1 : A photon has no rest mass, yet it carries definite momentum. 

Statement-2 : Momentum of photon is due to its energy and hence its equivalent mass. 

Equivalent mass of photon $\left(m\right)$ is given from equation:

$$\begin{gathered} E=m{c}^2=h\nu \\ \therefore m=\frac{h\nu }{c^2} \end{gathered}$$ 

where $E$ is energy, $m$ is mass, $c$ is speed of light, $h$ is Planck's constant, $\nu$ is frequency. 

$\therefore$ Momentum of photon $=\frac{h\nu }{c^2}\times c=\frac{h\nu }{c}$