Tourist visas, called visitor visas in the United States, are available for travelers from many countries who are coming for recreational or medical purposes. These visas are typically good for six months. Transit visas are available to foreigners who are simply passing through the United States or making a brief stop at a port or airport. Transit visa applicants must provide evidence that they will be in continuous transit to a foreign destination while in the United States. As of November 2012, both visitor visas and transit visas cost $160 per person, although additional fees may apply. Citizens of nearly 40 countries are allowed to travel in the United States without a visa under the Visa Waiver Program.
No. If your visa is valid and unmarked or undamaged, you can travel with your two passports together (old and new), if the purpose of your travel matches your current nonimmigrant visa. Also, the name and other personal data must be the same in both passports (unless the name change was due to marriage), and both passports must be from the same country and of the same type (i.e., both tourist passports and both diplomatic passports).
All nationals listed in the chart above are eligible to apply online for an e-Tourist Visa (eTV). You must apply at least four days before you arrive in India. You can only enter India via those airports listed on the eTV website. There are five e-Visa subcategories: e-Tourist visa, e-Business visa, e-Medical visa, e-Medical Attendant Visa and e-Conference Visa.
In general, to obtain a visa it will take four business days. To get a visa in 2-3 business days you can apply for the Express Service (it costs an additional 20 USD); while to get a visa within one business day you can apply for Rush Service (which costs an additional 30 USD). Note that the Rush Service is granted only in documented cases of extreme urgency.