7. Formation of day and night is a periodic change. Explain it.

Part 1: Periodic change

• The changes that occur after a regular interval of time are called periodic changes.
• Changes of seasons, the beating of the heart, etc. are some examples of periodic changes.

Part 2: Formation of day and night is a periodic change

• The rotation of the earth in its own axis results in the formation of day and night.
• It is a periodic change because it is repeated after a regular interval of time.