Note that in all the above experiments, it is found that, if frequency of
the incident radiation exceeds the threshold frequency, the photoelectric
emission starts instantaneously without any apparent time lag, even if
the incident radiation is very dim It is now known that emission starts in
a time of the order of 10– 9 s or less We now summarise the experimental features and observations
described in this section (i)
For a given photosensitive material and frequency of incident radiation
(above the threshold frequency), the photoelectric current is directly
proportional to the intensity of incident light (Fig