I got my US B1 visa last month on my Indian passport. Someone in my family wrote a phone number on one of the blank page of my passport. As my passport is damaged now, can I travel with my current passport to US or I should apply for new passport? Also, will B1 visa be valid on old damaged passport if I get new passport?
The US Consulate in Chennai has this to say about visas in damaged passports:
You may travel carrying your old and new passports if the visa in your old passport is valid and not damaged. If the old passport is in poor condition, or if the visa in your old passport is damaged, you should apply for a new visa. You cannot transfer your old visa to the new passport. To apply for a new visa, please schedule an appointment and come in for a personal interview, remembering to bring all relevant documents. We can formally cancel the damaged old visa at the time of the new application.
India classes passport damage into two classes: damaged, and damaged beyond recognition (which means that your personal information page is damaged or unreadable). Some writing on one of the blank pages probably does not qualify as damage, though. Passports tend to accumulate lots of writing and stamps on all of their blank pages; that's the point of them! So you can probably travel on it.
If you do decide to replace the passport: If your passport is merely damaged, and not damaged beyond recognition, and the visa is not damaged, you should be OK to travel with your new passport and the visa in the old passport.