please suggest some good books and online websites for basic concepts of spectroscopy
That's a huge field, with specialized information for various parts of the electromagnetic spectrum. (Nuclear) Magnetic spectroscopy is another huge field with it's own specialized techniques. There's also force spectrosopy, (time-dependent) fluorescence spectroscopy, and I'm sure many others.
First, you need to be more specific, otherwise you will get lost quickly.
What have you pulled off the shelf at your local library?
i have taken mircowave spectroscopy book.actually what is mircowave spectroscopy?
Microwave spectroscopy is like any other electromagnetic spectroscopy- one is interested in how materials interact with electromagnetic radiation over a certain waveband. Microwave spectroscopy is generally used for gases- the spectrum is very interesting because of the material properties probed (rotational transitions), the astrophysical relevance, and the ability to coherently manipulate the signal (i.e. control the phase). There's probably modern applications in telecommunications as well.
are u interested in any specific spectroscopy topic?
or browse spectroscopynow.com
Separate names with a comma.