Figure 14.23 represents the layout of Lloyd’s mirror experiment. S is a point source emitt...

Figure 14.23 represents the layout of Lloyd’s mirror experiment. S is a point source emitting waves of frequency 6 × 1014 sec-1. A and B represent the two ends of a mirror placed horizontally and LOM represents the screen. The distances SP, PA, AB and BO are 1 mm, 5 cm, 5 cm and 190 cm respectively. (a) Determine the position of the region where the fringes will be visible and calculate the number of fringes. (b) Calculate the thickness of a mica sheet (n = 1.5) which should be introduced in the path of the direct ray so that the lowest fringe becomes the central fringe. The velocity of light is 3 × 1010 cm/sec.