What is density of population? Give India’s population distribution by density with the reasons responsible for the same.

Density of population is calculated as the number-of persons per unit area. The population density of India in 2001 was 324 persons per sq. km.
(i) Regions with sparse population density: Rugged terrain and unfavourable climatic conditions are primarily responsible for sparse population in these areas. For example, Jammu and Kashmir, Arunachal Pradesh and Mizoram.
(ii) Regions with moderate population density: Hilly, dissected and rocky nature of terrain, moderate to low rainfall, shallow and less fertile soils hate influenced the population densities in these areas. For example, Assam and peninsular states.
(iii) Regions with high density of population: These areas have high population density because of the flat plains with fertile soils and abundant rainfall. For example, Northern plains and Kerala.