What is it about the national flag and national anthem that brings that undeclared emotion within us, wonders Amitabh Bachchan who recently shot a scene for "Satyagrah" holding the Tricolour.

Apparently the megastar's role in the Prakash Jha directed film is modelled on activist Anna Hazare and he felt proud to shoot the film with the national flag in hand.

"What is it about National Flags and National Anthems, that brings that undeclared emotion within us? Why is it that when we hold our tricolor, sing our 'Jan gan man...', that we choke with emotion, " he wrote on his blog.

"What makes those hardened athletes, that stand on the victory podium during the Olympic medal ceremony, drop a tear as their nations' flag climbs up on the flagstaff in a stadium filled to capacity, " he wondered.

He also posted exclusive "tabs" of the shoot on his Facebook page and said that such activities are needed for the "documentation of our industry".

"Some special tabs have been put up on the Facebook site, do have a look at it and join in... it is more now to design and record associations or stories linked to various films of mine through the years..., " he posted.