Question

This is an apparatus for studying the photoelectric effect. The work function of the material being investigated is 3.5 × 10–19 J. The battery is set at 1.5 V. What is the longest wavelength of light needed to produce an electric current from the cathode (C) to the anode (A)?

Answer 1

The longest wavelength of light needed to produce current is 567.9 nm.

Step-by-step 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

`E = (hc)/(\lambda)`

where;

c is speed of light = 3 x 10⁸ m/s

λ is the longest wavelength of light needed to produce current

`E = (hc)/(\lambda) \\\\\lambda = (hc)/(E) \\\\\lambda = ((6.626* 10^(-34))(3* 10^8))/(3.5* 10^(-19))\\\\\lambda = 5.679 * 10^(-7) \ m\\\\\lambda = 567.9 * 10^(-9) \ m\\\\\lambda = 567.9 \ nm`

Therefore, the longest wavelength of light needed to produce current is 567.9 nm.