Sin is where the glory of God is absent………..

“The [basis of the] judgment (indictment, the test by which men are judged, the ground for the sentence) lies in this: the Light has come into the world, and people have loved the darkness rather than and more than the Light, for their works (deeds) were evil.

For every wrongdoer hates (loathes, detests) the Light, and will not come out into the Light but shrinks from it, lest his works (his deeds, his activities, his conduct) be exposed and reproved.

But he who practices truth [who does what is right] comes out into the Light; so that his works may be plainly shown to be what they are--wrought with God [divinely prompted, done with God's help, in dependence upon Him].”                    John 3:19-21 AMP

John 3:19 implies that the world has no light therefore it needs the light to shine into it. When the light shines, it comes to influence, illuminate and change the world.

When Jesus proclaims we are the light of the world, there are three principles: (1) the world is dark so our existence has value because we are the light of the world, (2) Christians need to live a dynamic not passive life TO influence instead of constantly being influenced by the world and (3) we need to be self-sacrificing moment by moment to bless others.

When the candle is burning giving light it is actually burning itself.

What does it mean when the Bible say God is light?  It says the light will go into darkness and influence all that is dark.  It will never be influenced by darkness. Light can chase away darkness.

What is the relationship between light and darkness?

There are a few possibilities: (1) Light chase darkness so darkness runs away, (2) darkness hides because it is afraid of the light, (3) darkness is destroyed by the light.

If darkness escapes when light comes, is it escaping at the same speed of light?

If they are the same speed, then wherever light comes darkness disappears at the same time.

We know that darkness is the absence of light therefore sin is where the glory of God is absent.

Because the deeds of men are evil they love darkness rather than light.  It is unnatural for darkness to reject light.  In nature, wherever there is light darkness would surrender.  But spiritually, Jesus (the Light) was rejected by men who lived in darkness because the deeds of men were evil.

People who are seeking God want to be in the Light all the time, letting the Light expose their thoughts, words, and deeds.  They know that there is nothing beneficial about the darkness, so they want every part of their lives exposed by the Light.  

They want to see if their deeds are “wrought in God”-- performed in God's will and by His power, instead of in the flesh (in human strength, in self-centeredness, seeking praise from others).

 People who are born of the Spirit are to live in the power of the Spirit, letting the Spirit of Christ do His works through them.

John 6:63 "It is the Spirit who gives life; the flesh profits nothing….”

John15:5 "I am the vine, you are the branches; he who abides in Me and I in him, he bears much fruit, for apart from Me you can do nothing.”