If you observe that it is a custom that we have to light a lamp in each and every house at India.Even if you see in some Indian homes a lamp is lit daily before the altar of the Lord. In some houses it is lit at dawn, in some, twice a day and in a few it is maintained continuously which is called as Akhanda Deepa. All auspicious functions commence with the lighting of the lamp, which is often maintained right through the occasion.Light symbolizes knowledge, and ignorance darkness. The Lord is the Chaitanya who is the source, and gives knowledge. Hence light is worshiped as the Lord himself.I hope all of you know that if we have knowledge on one thing,definitely we don't fear when things go wrong.It removes darkness. Also knowledge is a lasting inner wealth by which all outer achievement can be accomplished. Hence we light the lamp to bow down to knowledge as the greatest of all forms of wealth.Why not light a bulb or tube light? That too would remove darkness. But the traditional oil lamp has a further spiritual significance. The oil or ghee in the lamp symbolizes our vaasanas or negative tendencies and the wick, the ego. When lit by spiritual knowledge, the vaasanas get slowly exhausted and the ego too finally perishes. The flame of a lamp always burns upwards. Similarly we should acquire such knowledge as to take us towards higher ideals.
Whilst lighting the lamp we thus pray:
Deepajyothi parabrahma
Deepa sarva tamopahaha
Deepena saadhyate saram
Sandhyaa deepo namostute