d. Why do you use light-aarti to pray?

Lamps were the only source of artificial light in olden days. Consider a dark room, where God, a symbol/representation of the divine, is placed (in the sanctum of temples). The priest shows a lamp in the form of Aarathi close to the murti. The purpose is to make sure the picture is registered in our minds.
Light represents knowledge. When praying we are saying that the Lord gives me enough knowledge all the time.

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Contributor: Dr. Jyoti Lulla

Location of this post (18d): https://www.hinduspeakers.org/ufaqs/why-do-you-use-light-aarti-to-pray/