Lumos

Question: A photon starts moving in the random direction from the center of the square of size 3. Let’s say it first colloids to the glass wall AB. What is the expected distance traveled by the photon before hitting the wall AB again? . . C A P T A I N I N T … Continue reading Lumos

100 balls

Question: You are given an urn with 100 balls (50 black and 50 white). You pick balls from urn one by one without replacements until all the balls are out. A black followed by a white or a white followed by a black is "a colour change". Calculate the expected number of colour changes if … Continue reading 100 balls