1. The problem statement, all variables and given/known data Consider a random walker in one dimension, which can take right or left steps with equal probability. Assume that the walker starts at the location k>0 and there is an absorbing wall at point labelled as 0, that means if the walker reaches 0 the process stops and he stays there. Calculate the probability of reaching point m>0 in N steps. By taking continuum limit, find the solution to the diffusion in the presence of an absorbing wall at the origin. 3. The attempt at a solution Actually this is an example of reflection principle (method of imagines boundary value problems.) However I couldnt figure out how its related. So if you give me hint to where should I start I'll be appreciated.