Threshold frequency for a metal is 10^ 15 ~Hz. Light of =4000 A f… - Vidyadip

MCQ

Threshold frequency for a metal is $10^{15} \mathrm{~Hz}$. Light of $\lambda=4000 \mathring A$ falls on its surface. Which of the following statements is correct

✓
No photoelectric emission takes place
B
Photo-electrons come out with zero speed
C
Photo-electrons come out with $10 \mathrm{~m} / \mathrm{sec}$ speed
D
Photo-electrons come out with $10 \mathrm{~m} / \mathrm{sec}$ speed

✓

Answer

Correct option: A.

No photoelectric emission takes place

Frequency of light of wavelength $(\lambda=4000 \mathring A)$ is $v=\frac{c}{\lambda}=\frac{3 \times 10^8}{4000 \times 10^{-10}}=0.75 \times 10^{15}$ which is less than the given threshold frequency.
Hence no photoelectric emisssion takes place.

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