Question

A laser is producing monochromatic light which is used to eject electron from the sheet of gold having threshold frequency $6.15\times {10}^{14}{s}^{-1}.$ Which of the following incident radiation are not suitable for the ejection of electron?

• A. 1.5 moles of photons having frequency $3.05\times {10}^{14}{s}^{-1}$
• B. 0.5 moles of photon of frequency $12.3\times {10}^{12}{s}^{-1}$
• C. One photon with frequency $5.16\times {10}^{15}{s}^{-1}$
• D. All of the above

Answer 1

Answer: (A), (B)

0.5 moles of photon of frequency $12.3\times {10}^{12}{s}^{-1}$

The interaction between photon and electron is always one to one for ejection of photoelectrons i.e one photon will always eject one electron only. So, increase in number of photons will only increase the photocurrent, but the ejection of electrons only takes place when the frequency of incident radiations is greater than threshold frequency.
$h{\nu }_0<h\nu$ or
${\nu }_0<\nu$ where ${\nu }_0=$ threshold frequency and $\nu =$ incident frequency
Which is only in case of (c)