A monochromatic point source S radiating wavelength 6000A° with power 2 watt an aperture A of diameter 0.1m and a large screen SC are placed as shown in the fig. A photoemissive detector D of surface area 0.5cm^2 is placed at the center of the screen. The efficiency of the detector for photoelectron generation per incident photon is 0.9.a) Calculate the photon flux at the center of the screen and the photocurrent in the detector.b) If a concave lens L of focal length 0.6m is inserted in the aperture as shown, find the values of photon flux and photocurrent. Assume uniform average transmission of 80℅ from the lens.c) If the work function of the photoemissive surface is 1ev, calculate the value of the stopping potential in the two cases (without and with lens in the aperture)
Mvskm Srinivas , 7 Years ago
Grade 11
