• # question_answer Light of wavelength $\lambda$ strikes a photo sensitive surface and electrons are ejected with kinetic energy E. If the kinetic energy is to be increased to 2E, then the wavelength must be changed to $\lambda ,$where A) $\lambda >\lambda$ B) $\lambda =\frac{\lambda }{2}$ C)  $\lambda =2\lambda$ D)  $\frac{\lambda }{2}<\lambda <\lambda$

We have, ${{E}_{k}}=\frac{hc}{\lambda }-\text{o}{{|}_{0}}$ and $2{{E}_{k}}=\frac{hc}{\lambda }-\text{o}{{|}_{0}}$ By the two relations, we have $\lambda >\frac{\lambda }{2}$ and $\lambda <\lambda$ So, $\frac{\lambda }{2}<\,\lambda <\lambda$