Well I feel aditi's approach is okie dokie.......that must be it........

for the 3rd question..............Charge densities shud be equal but opposite in signs...

@ Pantpranv...i said the same thing quite earlier.......

and

Mr. Ultimator.....Laws are made on the basis of observations...from which some assumptions are made and formulated and then stated as the laws.......Mr. Coulomb did that and u read that in ur textbook.....

from what he did....I just interpreted it in another way that cud become the answer for above question.....

and thus if u wanna say that i m wrong.....then u mean Mr Coulomb is wrong.....and if u r saying this then their is no use for u in studying Physics....u make ur own Physics and do that.....ok......mind it.......

I dont want myself to be controlled by someone else....this is what it means........i think so/////

answer i m getting is.........

.......posting the complete soln....

see guys........

every charge has some electric field around it...Posistive charge has an outgoing field while a negative charge has an incoming field.........as if we take same types of charges...then their respective fields are not satisfied...but if we take opposite charges they mutually satisfy each others field and thus its stated that.........

Like charges repel and Opposite charges attract.......

for third question just use simply mirror formula........

for fourth question diagram attached........

for fifth question.....I will tell u the concept then u can easily figure it out........

whenever light travels from an optically denser medium to a rarer medium....it bends away from the normal..and vice-versa......this happens because of the different speeds of light in different media...