Question

All electrons ejected from a surface by incident light of wavelength 200 nm can be stopped before travelling 1 m in the direction of uniform electric field of 4N/C. The work function of the surface is–

• A. 4eV
• B. 6.2 eV
• C. 2 eV
• D. 2.2 eV

Answer 1

Answer: (D)

2.2 eV

Answer 2

V_s = E.d

V_s = 4Volt

eV_s = $\frac { 12400 } { \lambda }$W

4 eV = $\frac { 12400 \mathrm { eV } } { 2000 }$ – W

4eV = 6.2eV – W [W = 2.2 eV]