But when anything is exposed by the light, it becomes visible, for anything that becomes visible is light. Therefore it says,“Awake, O sleeper, and arise from the dead, and Christ will shine on you.” (Ephesians 5:13-14 ESV)
How do you see? We see an object when light reflected off it’s surface enters our eyes and is translated into an image by retina and nerves. The light does not usually come from the object itself, mostly it is from the sun in daytime. As the light shines it reveals to our eyes all that was hidden by darkness.
As Christ shines in the darkness (John 1:5) the true light reveals all. People will see who I am as Christ shines upon me. If my life is pure and holy they will see Christ clearly reflected through my life with minimal distortion. If I am corrupt and filthy they will see me clearly for what I am — Christ’s glory will remain brilliant, my filth will be starkly illuminated against his holiness.