4.4.6　Analysis and questions

(1)What is the work function of electrons?If WS=2.0 eV is used to make the cathode of a phototube,what is the red limit of the wavelength that can be detected?

(2)How to accurately find the cut-off voltage from the volt-ampere characteristic curve of the photocell?

(3)What is dark current?What is the reason of causing it?(https://www.daowen.com)

(4)What is the cause of the reverse current?How to eliminate the influence of the reverse current in the experiment?

(5)Describe the structure and principle of blazed grating and the principle of monochromator spectroscopy.