Question

Utilizing the photoelectric effect, a student fund that it required light with a maximum wavelength of 351 nm to dislodge electrons from a polished zinc metal surface. A) What is the work function of this metal in joules? B) what is the velocity, in m.s-1, of the ejected electron when incident radiation of 298 nm is used (hint: me = 9.11 x 10 -31kg ). I dont need just the answer, I got this wrong and need to know how to do it.

Answer 1

A)

we have:

wavelength = 3.51*10^-7 m

we have below equation to be used:

Energy = Planck constant*speed of light/wavelength

=(6.626*10^-34 J.s)*(3.0*10^8 m/s)/(3.51*10^-7 m)

= 5.663*10^-19 J

Answer: 5.66*10^-19 J

b)

we have:

wavelength = 2.98*10^-7 m

we have below equation to be used:

Energy = Planck constant*speed of light/wavelength

=(6.626*10^-34 J.s)*(3.0*10^8 m/s)/(2.98*10^-7 m)

= 6.67*10^-19 J

This is incident energy

KE = E - Eo

= 6.67*10^-19 J - 5.66*10^-19 J

= 1.01*10^-19 J

Now use:

KE = 0.5*m*v^2

1.01*10^-19 = 0.5*(9.11*10^-31)*v^2

v^2 = 2.217*10^11

v = 4.71*10^5 m/s

Answer: 4.71*10^5 m/s