Science and Technology: For Civil Services Preliminary and Main Examinations About the Author Dr. Ravi P. Agrahari, a Ph.D. from IIT, Delhi, is a recipient of Junior Research Fellowship and Senior Research Fellowship from CSIR, Government of India. He has been working as a research scientist in IIT, Delhi since 2015. Mr. Agrahari also works as an independent consultant in the fields of environment, renewable and sustainable energy and biogas issues at the Bag Energy Research Society, Varanasi. He is an energy expert and has published various papers in many reputed international journals. He has attended many international conferences in Sweden and France. Dr. Agrahari is well-known for his expertise in “Environmental Sciences” and “Science and Technology” and has authored several books on the same for UPSC examination. He has been teaching UPSC and CSIR/UGC-NET/GATE aspirants for more than 17 years. During his 17 years long teaching experience, he has taught in more than 50 reputed coaching institutes for Civil Services Examinations in more than 15 states in India.