Understanding the population growth patterns of a country is crucial for planning and development. India's population history is often divided into several distinct phases based on demographic characteristics.

India's Population Growth Phases

India's demographic transition can be broadly categorized into four phases:

• Phase I: Stagnant Population (1901-1921) - Characterized by high birth rates and high death rates, resulting in very low population growth. This period saw outbreaks of diseases, famines, and poor health facilities.
• Phase II: Steady Population Growth (1921-1951) - Death rates started declining due to improvements in health and sanitation, while birth rates remained high. This led to a steady increase in population. 1921 is sometimes referred to as the "Year of Great Divide" as it marked the beginning of this phase of slow but steady growth.
• Phase III: Population Explosion (1951-1981) - This period witnessed a rapid and significant increase in India's population. This is often termed the period of population explosion.
• Phase IV: High Growth with Signs of Slowing Down (Post 1981 till present) - Although the population continued to grow rapidly, the growth rate started showing a declining trend. This is due to a gradual decrease in the birth rate.

Identifying the Period of Population Explosion

The question asks specifically for the period referred to as the period of population explosion in India. Looking at the options and the historical demographic trends, the period from 1951 to 1981 stands out as the phase of most rapid population increase.

During the period 1951-1981, several factors contributed to this explosion:

• Significant improvements in healthcare and sanitation led to a sharp decline in mortality rates (death rates).
• Life expectancy increased considerably.
• Birth rates remained relatively high.
• The gap between birth rates and death rates widened significantly, leading to a very high natural increase in population.

This accelerated growth rate is why the period 1951-1981 is specifically identified as the period of population explosion in India.

Analyzing the Options

Let's briefly look at the other options in the context of India's population history:

• Post 1981 till present: While the population continued to be large and grow, the rate of growth started to slow down compared to the previous period.
• 1901 - 1921: This was a period of stagnant or even slightly declining population growth due to high mortality.
• 1921 - 1951: This was a period of steady, but not explosive, population growth compared to the 1951-1981 phase.

Therefore, the period 1951 - 1981 accurately represents the phase of population explosion in India.

Revision Table: India Population Milestones

Additional Information: Causes and Consequences of Population Growth

Rapid population growth, especially during the period of population explosion, can have significant impacts. Some causes and consequences include:

Causes:

• Decrease in death rate due to improved healthcare, control of epidemics, and better sanitation.
• High birth rate due to factors like early marriages, lack of awareness about family planning, social customs, and economic conditions.

Consequences:

• Increased pressure on natural resources like land, water, and forests.
• Challenges in providing adequate infrastructure, education, and healthcare.
• Potential for increased unemployment and poverty.
• Strain on the environment due to increased consumption and waste.

Understanding the population explosion period helps in analyzing the root causes of many socio-economic and environmental challenges India faces.