Photoelectric Effect Problem (1 Viewer)

[XcarvengerX]

I have problem with this question:

A scientist is investigating the effect of different types of radiation on the surface of a piece of sodium metal. The two variables under investigation will be the frequency and the kinetic energy of the photoelectrons.
(i) Should the sodium plate be positively or negatively charged?
(ii) Results for teh experiment are as follow:
Frequency of incident light............Stopping potential
(X 10¹⁴ Hz)............................................(volts)

5.4.......................................................0.45
6.8.......................................................1.00
7.3.......................................................1.15
8.1.......................................................1.59
9.4.......................................................2.15
11.9.....................................................2.91

Record these results on a KE_max versus frequency graph.

(iii) Determine the threshold frequency for the sodium metal
(iv) Determine the value for Planck's constant, h, from your graph.
(v) What is the work function for sodium?



So basically I don't know what type of graph I should draw because I can't work out the kinetic energy from information given. I think part (i) is positive. Please help with the other parts especially the graph.

Thanks.

 

[tennille]

I'd draw a line graph. That was the standard graph we did in high school. To work out max KE, you use stopping voltage * e (the charge of the electron). The threshold frequency is the value of the frequency when the kinetic energy is zero (ie. the x axis). Planck's constant is the gradient of the graph. The work function is the value of Kinetic Energy when the frequency is zero (ie. the y-axis).

 

[rama_v]

Kinetic energy is just referring to the energy of the ejected electrons. Hence 1/2 * mass(electron) *v^2 but that is equal to the stopping potential, eVo (via the work-energy theorem - but dont worry, the theorem is not in the hsc).