Photoelectric effect and frequency

[briteliner]

Homework Statement

the wavelengths of visible light range from about 380 nm to 750 nm. what is the range of photon energies (in eV) in visible light? a typical fm radio station's broadcast frequency is about 100Mhz. what is the energy of an FM photon of the frequency?

Homework Equations

eV_o=hf-(phi)
phi=hf_o
i don't know how to get f_o which is the threshold frequency. that's the only part I am stuck with

The Attempt at a Solution

i don't know how to get fo which is the threshold frequency.

 

[gabbagabbahey]

The energy of a photon of frequency [itex]f[/itex] is given by [itex]E=hf[/itex].

[itex]eV_0=hf-hf_0[/itex] allows you to determine the difference in electric potential necessary to make electrons in a material with a threshold frequency [itex]f_0[/itex] to emit photons of frequency [itex]f[/itex]. This equation is useless to you here. You are simply asked to determine the energies of photons of a given wavelength or frequency.