Passage V
Fora photon to free an electron from a metal, the photon's frequency, f, must equal or exceed the threshold frequency, fT, for the metal. If f > fT, the photon has extra energy that is transferred to the electron as kinetic energy, resulting in the ejection of the electron from the metal. Kmax is the highest kinetic energy an ejected electron can have for a given f.
Table 1 displays fT for the metals calcium (Ca), magnesium (Mg), mercury (Hg), and platinum (Pt). Figure 1 is a graph of Kmax versus f for each of the 4 metals. Figure 2 is a graph of a photon's energy versus its f.
25. Based on Figure 1, which of the following correctly ranks Ca, Mg, and Pt in order of increasing Kmax at f = 16.0 x 1014 Hz?
Your Answer is
Correct Answer is A
Explanation
Looking at figure 1, when the abscissa is 16.0, the ordinate corresponding to Ca has exceeded 6.0, the ordinate corresponding to Mg is about 4.7, and the ordinate corresponding to Pt is about 2.0, so Kmax should be arranged from small to large Pt, Mg, Ca