How are FDs taxed?

Interest earnings from your fixed deposit are taxed as per your tax slab under the head "Income from Other Sources". 

For example, if you are in a 20% tax bracket and you booked a 1-year FD of Rs 1 lac at 9% interest rate. You will get a total interest for the year of Rs 9000. 

The tax that you will have to pay while filing tax will be 20% of 9000 = Rs 1800.