Answer :

Some time we observe that the marks of chalk on the black board could not be wiped out easily after a long time. This happens because of the diffusion of particles of chalks with the particles of black-board and marks of chalk could not be wiped out.

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation
view all courses