Hi everyone! I've got a question. I have this problem and I want some help because I couldn't with it.

The threshold frequency for shedding an electron from the cesium surface

metallic is 5.18 x 10¹⁴ s⁻¹. Calculate:

- The energy of a photon of this frequency

- The energy of a photon of light of wavelength 400 nm
- The kinetic energy of an electron that gives off cesium from the surface

a beam of light with a wavelength of 400 nm.

For the first one I used the equation

**E=hv**, for the second I used

**E = h*c/λ** and the last one

**kinetic energy = h (photon frequency - threshold frequency)**But I get negative kinetic energy

**(-3.93x10⁻¹⁹ to be exacts)**. Am I doing something wrong? How would it be the right way to solve this problem?

Thank you for taking the time to read and answer me<3!