Answer :
Answer:
Threshold frequency for sodium metal is [tex]5.49\times 10^{14}\ s^{-1}.[/tex]
Explanation:
We know, relation between threshold frequency , kinetic energy and frequency is given by :
[tex]K.E=hv-hv_o[/tex]
Here h is plank's constant and [tex]v_o[/tex] is threshold frequency .
Given :
Frequency of photon , [tex]v=6.66\times 10^{14}\ s^{-1}.[/tex]
Kinetic energy of electron , [tex]K.E=7.74\times 10^{-20}\ J.[/tex]
Putting all these value in above equation we get :
[tex]7.74\times 10^{-20}=(6.66\times 10^{14}-v_o)\times 6.626\times 10^{-34}\\\\v_o=5.49\times 10^{14}\ s^{-1}.[/tex]
Hence , this is the required solution .