Threshold frequency for a metal is ${10^{15}}Hz$. Light of $\lambda = 4000{ \mathring A}$ falls on its surface. Which of the following statements is correct
- ANo photoelectric emission takes place
- BPhoto-electrons come out with zero speed
- CPhoto-electrons come out with $10^3 m/sec$ speed
- DPhoto-electrons come out with $10^5 m/sec$ speed
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