(a) According to Einstein, the energy of photon is given by
$E = hv = \frac{hc}{\lambda}$
Where $h$ is Planck’s constant, $c$ the speed of light and $\lambda\ the\ wavelength.$
$\therefore\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \frac{E_{1}}{E_{2}} = \frac{\lambda_{2}}{\lambda_{1}}$
Given, $\lambda_{1} = 150\ nm\ ,\ \lambda = 300$nm
$\therefore\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \frac{E_{1}}{E_{2}} = \frac{300}{150} = \frac{2}{1}\ $