On which date did the Constitution of India come into force and begin to operate as the supreme law of the country?

Introduction / Context:
The adoption and enforcement of the Constitution of India mark a turning point in the country political and legal history. While India attained independence on one date, the Constitution was adopted on another date and came into force on yet another date. This question focuses on the specific day when the Constitution actually started operating as the supreme law of the land, a critical fact in Indian polity and history.

Given Data / Assumptions:

The options include 15 August 1947, 26 January 1950, 26 November 1948 and 6 November 1948.
You are asked to identify the date on which the Constitution came into force, not the date of independence or the date of adoption by the Constituent Assembly.
It is assumed that you know that the dates of independence, adoption and enforcement are different but related milestones.

Concept / Approach:
India became independent from British rule on 15 August 1947. The Constituent Assembly adopted the Constitution on 26 November 1949. However, the Constitution came into force on 26 January 1950, a date chosen to commemorate the declaration of Poorna Swaraj by the Indian National Congress in 1930. This enforcement date is what transformed India into a sovereign democratic republic with a fully operative constitutional framework. Therefore, the correct approach is to distinguish between these three key dates and pick 26 January 1950 as the date the Constitution came into effect.

Step-by-Step Solution:
Step 1: Recall that 15 August 1947 is celebrated as Independence Day, marking the end of British colonial rule, but at that time the Constitution was still being drafted. Step 2: The Constitution was adopted by the Constituent Assembly on 26 November 1949, which is sometimes observed as Constitution Day, but adoption is not the same as enforcement. Step 3: The Constitution came into force, or commenced, on 26 January 1950. This is the day when India began functioning as a republic under its own Constitution, and it is celebrated as Republic Day. Step 4: The other dates in 1948 listed in the options do not correspond to the adoption or enforcement of the Constitution and are distractors. Step 5: Therefore, the correct date on which the Constitution came into force is 26 January 1950.

Verification / Alternative check:
History and polity textbooks always state that independence came in 1947, adoption took place in November 1949, and enforcement on 26 January 1950. Republic Day celebrations on 26 January every year commemorate the enforcement date, highlighting its significance. This three date sequence is so fundamental that it appears in nearly all exam syllabi, confirming that 26 January 1950 is the only correct answer for the enforcement date.

Why Other Options Are Wrong:
15th August 1947: This is Independence Day, the date when India ceased to be a British colony, but the Constitution had not yet been adopted or enforced. 26th November 1948 and 6th November 1948: These dates do not correspond to the adoption or enforcement of the Constitution. The adoption occurred in November 1949, not 1948.

Common Pitfalls:
A common error is to mix up the adoption date (26 November 1949) with the enforcement date, or to assume that independence and constitutional enforcement took place on the same day. To avoid this, remember the simple sequence: independence on 15 August 1947, adoption on 26 November 1949 and enforcement on 26 January 1950. After that final date, India functioned fully under its own supreme Constitution.

Final Answer:
The Constitution of India came into force and began to operate as the supreme law of the country on 26th January 1950.