26、( )電氣設備裝有地線之目的為(A)防止電擊(B)防止火災及爆炸(C)啟動保護設備(D)以上皆是

1. A beam of light with an intensity of 15 W is. incident on a copper plate (work function is7.43xl0-19 J). Electrons with a minimum wavelength of 3.75x10 －10 m are ejected from the surface of the copper. Calculate the frequency of the incident light. [Hint: Plank constant = 6.626 x 10－34J·s] (A)3.7lx1015Hz (B) 3.71 x 1016 Hz,(C) 3.71 x 1017 Hz,(D) 3.71 x 1018Hz(E) none of above