Answer:
The longest wavelength of light needed to produce current is 567.9 nm.
Explanation:
Given;
minimum energy required to produce electric current from the cathode to anode = work function, E = 3.5 x 10⁻¹⁹ J
E = hf
[tex]E = \frac{hc}{\lambda}[/tex]
where;
c is speed of light = 3 x 10⁸ m/s
λ is the longest wavelength of light needed to produce current
[tex]E = \frac{hc}{\lambda} \\\\\lambda = \frac{hc}{E} \\\\\lambda = \frac{(6.626\times 10^{-34})(3\times 10^8)}{3.5\times 10^{-19}}\\\\\lambda = 5.679 \times 10^{-7} \ m\\\\\lambda = 567.9 \times 10^{-9} \ m\\\\\lambda = 567.9 \ nm[/tex]
Therefore, the longest wavelength of light needed to produce current is 567.9 nm.
