明（ming, second tone）is composed with 日（ri, the fourth tone，the Sun) and 月（yue, also forth tone，the Moon). 　In ancient times，without electricity people could not see anything in the darkness without the light of the Sun or the Moon. So 明 means ‘brightness’, ’shining’.

白 （bai, the second tone) is also related to the Sun since its main part is 日. Then what is the top tilt stoke of 白? 　It should represent a beam of light from the Star that is enough for you see anything around with your naked eyes.

The phrase 明白 could be translated as ‘know, realize,see, understand，etc.’

I wish you have  understood　（明白）ｍｙ　explaining　about　明白！