How does Shakespeare bring together the contrasting images of light and dark in Romeo and Juliet?

One place in which images of light and
darkness are merged is in the famous
balcony scene. In particular, images of the
sun are used as images of light, while images of
nighttime, like the moon, are used as images of darkness. Shakespeare
uses the images of light and darkness for several reasons. One reason is to
symbolize the sexuality that is a dominant
theme.

Romeo's feelings of sexual
attraction for Juliet are especially expressed using light
and dark images in his opening soliloquy in
Act 2, Scene 2. He compares Juliet to the sun in order to
capture her beauty, as we see in his lines, "What light through yonder window breaks? /
It is the East, and Juliet is the sun!" (2-3). Since the sun is the brightest object in
the sky, comparing her to the sun describes her beauty as being glorious and bright,
just like the sun.

More importantly, he also uses
nighttime imagery to express his sexual desires for Juliet.
He uses an extended metaphor likening Juliet to the moon's
handmaiden, telling her in his mind to kill the moon and cease being her
handmaiden. The moon literally refers to the Roman goddess Diana, goddess of the moon
and childbirth who is especially known for her vow of chastity. Hence, when he tells her
in his mind to cease being the moon's handmaiden, he is really telling her to
give up her chastity, which we especially see in his lines,
"[the moon's] vestal livery is but sick and green, And none but fools do wear it. Cast
it off" (8-9). Since vestal livery can be translated as virginal uniform or clothing,
Romeo is metaphorically in his mind telling Juliet to cast off her clothing.
The nighttime imagery is especially
significant because it is typically at nighttime when sexual activity
takes place. Hence these two images of light and darkness combine to paint
a provocative picture of Shakespeare's ongoing sexual
theme.