If the grain of the fact table and the dimension table are same then to get them at the different level of grain we introduce the bridge table between the fact and the dimension.

The statement is FALSE. Bridge tables are used to resolve many-to-many relationships between fact tables and dimensions, not to handle different grain levels. When grain levels differ between fact and dimension tables, you would typically create aggregate fact tables at the appropriate grain level or use conformed dimensions designed for multiple grains - not bridge tables.