A rook and king can give checkmate while a bishop and king or knight and king cannot.
Why is rook more powerful than bishop?
Why is rook more powerful than bishop because if we see the no of squares a rook can go to no of squares around it which a bishop can go is the same??
That's not true. A bishop can only reach half the squares. Which automatically explains why the rook is the stronger piece in most situations.

"Half the squares" is not accurate: a rook can always reach 14 squares (without obstacles in the way) while a bishop can reach anywhere between 7 and 13 squares depending on its position. All other considerations here cited are accurate, though.
EDIT: "Anywhere between" meaning 7, 9, 11, or 13.
"Half the squares" is not accurate: a rook can always reach 14 squares (without obstacles in the way) while a bishop can reach anywhere between 7 and 13 squares depending on its position. All other considerations here cited are accurate, though.
EDIT: "Anywhere between" meaning 7, 9, 11, or 13.
What is meant by "Half the squares" is that a bishop only ever has access to 32 squares, where as the rook can reach any of the 64 squares on the board.

Ah, I see. I thought we were talking about the reach on one move. Both are important considerations, I guess.

I must be missing something here.
It seems that if white had 2 rooks instead of 2 bishops, mate would be much easier/quicker and if black had a rook instead of that bishop, that piece would not be trapped. So yes, rook > bishop in most cases (except in extreme circumstances just like one can argue that pawn > rook or bishop on the 7th rank)

I must be missing something here.
It seems that if white had 2 rooks instead of 2 bishops, mate would be much easier/quicker and if black had a rook instead of that bishop, that piece would not be trapped. So yes, rook > bishop in most cases (except in extreme circumstances just like one can argue that pawn > rook or bishop on the 7th rank)
Following your logic. The following diagram proofs a Bishop is much stronger then a rook.

In that scenario, indeed it would be (heck a PAWN would be better than a rook in that scenario). Move the rook one space left or up to the dark squares (something a bishop could not do) and once again, the rook proves to be mightier.
Regardless, I'm sure we know in general what pieces are more valuable due to their power and mobility and in which scenario they are not. At least the OP's question was answered in the process of the thread as well.

Bishops or Rooks?
Imagine that u only got ur King & Rook/Bishop.. who could Chekmated?
I'll go for my Rooks.
Have you seen rooks go full pac-man mode on pieces? A bishop can only access 32 squares but rooks can access 64. And rooks are almighty in endgames( I think that is because rooks are located in corners and most people don't bother to develop them so they survive till the endgame). However, bishops can be better in some circumstances. For eg- your opponent is castled and you wanna mate them, so you line up your bishop and your queen on the same diagonal. This can be done with a rook but its harder.
Why is rook more powerful than bishop because if we see the no of squares a rook can go to no of squares around it which a bishop can go is the same??