SIGN CONVENSION

SPHERICAL MIRROR & SIGN CONVENTION

Sign Convention

A slip of paper is given to a person A who marks it either with a plus sign or a minus sign. The probability of his writing a plus sign is 1//3 . A passes the slip to B , who may either leave it alone or change the sign before passing it to C . Next C passes the slip to D after perhaps changing the sign. Finally D passes it to a refere after perhaps changing the sign. B,C,D each change the sign with probability 2//3 . The probability that the referee observes a plus sign on the slip if it is known that A wrote a plus sign is

A slip of paper is given to a person A who marks it either with a plus sign or a minus sign. The probability of his writing a plus sign is 1//3 . A passes the slip to B , who may either leave it alone or change the sign before passing it to C . Next C passes the slip to D after perhaps changing the sign. Finally D passes it to a refere after perhaps changing the sign. B,C,D each change the sign with probability 2//3 . If the refree observes a plus sign on the slip then the probability that A originally wrote a plus sign is

A slip of paper is given to a person A who marks it either with a plus sign or a minus sign. The probability of his writing a plus sign is 1//3 . A passes the slip to B , who may either leave it alone or change the sign before passing it to C . Next C passes the slip to D after perhaps changing the sign. Finally D passes it to a refere after perhaps changing the sign. B,C,D each change the sign with probability 2//3 . If the refree observes a plus sign on the slip then the probability that A originally wrote a plus sign is