Steinbeck employs the use of light at different points in the narrative to bring out the condition of loneliness. For example, Lennie wanders into Crooks' room because his light was on. Crooks' loneliness is illuminated because of light. In a very interesting take on this, it is because of the light that one realizes that Crooks is lonely. Yet, it is also because of the light that Crooks' loneliness is interrupted. He is no longer lonely when Lennie enters his room. Thus, the light is used to both accentuate loneliness and alleviate him from it.
This same paradoxical relationship between light and loneliness is seen in the death of Curley's wife. When Lennie kills Curley's wife, he immediately recognizes what he has done. He attempts to cover the body with hay. Once Lennie does this, he runs away and Steinbeck uses the description of light to illuminate an aspect of Curley's wife's, even though she is no more: "The sun streaks were high on the wall by now, and the light was growing soft in the barn." As this light grows, Steinbeck uses it to transform her now that she is dead:
Curley’s wife lay with a half-covering of yellow hay. And the meanness and the plannings and the discontent and the ache for attention were all gone from her face. She was very pretty and simple, and her face was sweet and young. Now her rouged cheeks and her reddened lips made her seem alive and sleeping very lightly. The curls, tiny little sausages, were spread on the hay behind her head, and her lips were parted.
The use of light growing on her dead body makes Curley's wife more human and more approachable than ever before. Light transforms her from being lonely to being alone, independent of the world and not dependent on its broken promises. Light is what brings out her ultimate loneliness because she is dead. Yet, light is also what transforms her to be distinct from a world where all she experienced was loneliness. Like Crooks, light brings attention to her loneliness, but also transforms it.