16. Among_______ , which one is ionic crystal?(A) NaCl, (B) SiO2, (C) CH4, (D) CO2 and (E) Fe

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