If the threshold frequency in the photoelectric effect decreases when the emitting metal is changed to a different metal, what can you say about the work functions of the two metals?

1 Answer
1s2s2p
Apr 18, 2018

The metal with the highest threshold frequency has the greatest work function.

Explanation:

Einstein's photoeletric equation is:
#hf=phi+1/2mv_"max"""^2#, where:

  • #h# = Planck's constant (#~6.63*10^-34Js#)
  • #f# = frequency (#Hz#)
  • #phi# = work function (#J#)
  • #m# = mass of an electron (#~9.11*10^-31kg#)
  • #v_"max"# = max velocity of the emitted electrons (#ms^-1#)

The threshold frequency is the frequency required for the electron to be released but have no kinetic energy.

#hf=phi#

#phiproptof#, so as the threshold frequency increases, the work function increases. The metal with the lower threshold frequency has the lowest work function.

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