Vishnu sahasranamam, slok30

Slok30:      Ojasthejo  DyuthiDharaha  Prakaasaathma  Prathaapanaha
               BuDdhaha  Spastaaksharo  Manthraha Chandraamsur BhaskaroDyuthihi 

The Bright  brillient Atma, which carrys  the Life force, the Radiation and  the  Light,; the valient, the Wise, the clarity,  the Imperishable, the Manthra, the Light in the  Moon and Sun, is sree Maha Vishnu.  

In this slok, Vishnu is  described as " Light", and the different  variations of
LIGHT.  " RADIENT, BRILLIENT, GLOW" are all in one way or the other, forms of
Light only.  Hence, Vishnu is an Atma, radiating  Intelligence, as light in all over universe. The physical format of Intelligence is Light only. ( Thejas ).
Vishnu is a " glowing Atma "(a devine field of attraction ), containing  total
Intelligence, ojas, vigour. This Radiation is the reason for the brightness  in  
     Sun and Moon.

Om Vishnave namaha