Answer: The threshold frequency of sodium metal is [tex]5.49\times 10^{14}s^{-1}[/tex] and no photoelectric effect is seen.
Explanation:
To calculate the threshold frequency, we use the equation:
[tex]E_k=h(\nu-\nu_o)[/tex]
where,
[tex]E_k[/tex] = kinetic energy of the light = [tex]7.74\times 10^{-20}J[/tex]
h = Planck's constant = [tex]6.626\times 10^{-34}J.s[/tex]
[tex]\nu[/tex] = frequency of the photon = [tex]6.66\times 10^{14}s^{-1}[/tex]
[tex]\nu_o[/tex] = threshold frequency of the sodium metal = ?
Putting values in above equation, we get:
[tex]7.74\times 10^{-20}=6.626\times 10^{-34}(6.66\times 10^{14}-\nu_o)\\\\\nu_o=5.49\times 10^{14}s^{-1}[/tex]
Photoelectric effect is defined as the emission of electrons when light hits the surface of metal. This effect will be seen only when the incident light fallen on the metal is greater than the threshold frequency of the metal.
We know that:
Frequency of orange light = [tex]5\times ^{14}s^{-1}[/tex]
It is visible, that frequency of incident light is less than the threshold frequency. So, the photoelectric effect will not be seen.
Hence, the threshold frequency of sodium metal is [tex]5.49\times 10^{14}s^{-1}[/tex] and no photoelectric effect is seen.
