A potential barrier of 0.4 V exists across a p-n junction. An electron enters the junction from the n-side with a speed of 6.0 × 10^5 ms^-1. The…

A potential barrier of $\displaystyle 0.4$ V exists across a p-n junction. An electron enters the junction from the n-side with a speed of $\displaystyle 6.0 \times 10^5 \mathrm{~ms}^{-1}$. The speed with which electron enters the p side will be $\displaystyle \frac{x}{3} \times 10^5 \mathrm{~ms}^{-1}$ the value of $\displaystyle x$ is \_\_\_\_. (Given mass of electron $\displaystyle =9 \times 10^{-31} \mathrm{~kg}$, charge on electron $\displaystyle =1.6 \times 10^{-19} \mathrm{C}$.)