How do I do (b) and (c)? Topic 2.3 Turning points (OPTION D)
2. When a metal surface is illuminated with light of wavelength 410 nm, photoelectrons are emitted with amaximum kinetic energy of 2.10 × 10−19 J.Calculate:
a the energy of a photon of this wavelength
b the work function of the metal surface
c the stopping potential for this surface illuminated by light of wavelength 410 nm
So for part
(a) E=hc/lambda =(6.63*10^-34)*(3*10^8)/410*10^-9
E=4.85*10^-19 j
then I thought
(b) work function = hf - Ek
=4.85*10^-19 - 2.10*10^-19
= 2.75*10^-19
but this is wrong textbook answer is 1.61*10^-19j
What am I doing wrong?