What is light? and how does it expose the deeds of darkness?
John 3:20-21 NKJV
For everyone practicing evil hates the light and does not come to the light, lest his deeds should be exposed. But he who does the truth comes to the light, that his deeds may be clearly seen, that they have been done in God.”
Here the deeds that are clearly seen are the deeds of the one who is coming to the light.
Note to self: ἀληθινόν has been translated as "true" yet the meaning in the days of Jesus meant "to be genuinely unconcealed"
Matt 5:16 NKJV
Let your light so shine before men, that they may see your good works and glorify your Father in heaven.
The result of Light is that good works may be seen.
2 Corinthians 4:6 NKJV
For it is the God who commanded light to shine out of darkness, who has shone in our hearts to give the light of the knowledge of the glory of God in the face of Jesus Christ.
Here Defined as: The knowledge of the glory of God.
Psalm 119:130 NKJV
The entrance of Your words gives light; It gives understanding to the simple."
The result of Light is that it gives understanding to the simple.
Acts 19:18 NKJV
And many who had believed came confessing and telling their deeds.
John 1:4 NKJV
In Him was life, and the life was the light of men.
Here light is connected to Life.
Luke 11:34 Clearly Explained Version
The life for your body is in your focus. When your focus is clear, unfolded, and on one agenda also all the body of you is full of life. However when your focus is toilsome with many agendas the body of you is dying.
I replaced out some analogies hoping to get a feel of the complete picture with Luke 11:34
Ephesians 5:11-13 NKJV
And have no fellowship with the unfruitful works of darkness, but rather expose them. For it is shameful even to speak of those things which are done by them in secret. But all things that are exposed are made manifest by the light, for whatever makes manifest is light.
Here Defined as: Whatever makes manifest.
Hebrews 11:31 NKJV
By faith the harlot Rahab did not perish with those who did not believe, when she had received the spies with peace.
I don't think it means snitching because Rahab the harlot did not snitch. And she was considered a woman of faith. But I do not know for sure.
Sources:  http://books.google.com/books?id=Gm1qJaJja1UC&pg=PA130&lpg=PA130&dq=%E1%BC%80%CE%BB%CE%B7%CE%B8%CE%B9%CE%BD%CF%8C%CE%BD+meaning&source=bl&ots=320epww5XX&sig=Mb0EwqcMJtnRq6wxhcWcWK7WVB8&hl=en&sa=X&ei=QNBHU8juFsSV2QW4-4CgBA&ved=0CFYQ6AEwBw#v=onepage&q=%E1%BC%80%CE%BB%CE%B7%CE%B8%CE%B9%CE%BD%CF%8C%CE%BD%20meaning&f=false