All electrons ejected from a surface by an incident light of wavelength 200 mm, can be stopped before travelling 1 m in the direction of a uniform electric field of 4N/C. What is the work function of the surface?
From photoelectric law:
V0=hce(1λ−1λ0)−(1)V0=E×d=4×1=4Vfrom(1):V0e=hcλ−hcλ0→hcλ0=W=hcλ−V0e=6.39×10−19J=4eV