Not everything is what it seems

Finding Nemo is a 2003 American computer-animated film produced by Pixar Animation Studios. It tells the story of the overly protective clownfish Marlin, who along with a regal tangcalled Dory, searches for his son Nemo. Along the way Marlin learns to take risks and to let Nemo take care of himself.

During their adventure searching Nemo, Marlin and Dory are involved in a struggle with an anglerfish in the deep sea. This scene is very interesting because light, usually associated with positive and reassuring situations, in this case reveals a terrible and scaring one.

Life depends on a beam of light

'I Am Legend' is a 2007 post-apocalyptic science fiction film directed by Francis Lawrence

In September 2012, after a lethal worldwide epidemic, Robert Neville (Will Smith) is left as the last healthy human in New York City.

Only 12 million people were naturally immune to the virus. The rest degenerated into bald, pale, aggressive beings referred to as 'Darkseekers', who hunted down the immune humans as prey. The 'Darkseekers' are so-called for hiding in buildings and dark places during the day due to a painful intolerance to UV radiation.

In this scene, the protagonist and his dog can escape from the 'Darkseekers' thanks to a beam of light that is like a barrier between them and the others.
But it's the sunset and the beam of light is getting smaller...

The 'Force' and the dark side

In the epic space opera 'Star wars' (first movie in 1977) light and dark symbolize the contrast between good and evil. 

One of the prominent elements of Star Wars is the 'Force', an omnipresent energy that can be harnessed by those with that ability. It is described in the first produced film as 'an energy field created by all living things [that] surrounds us, penetrates us, [and] binds the galaxy together'.

The Force allows users to perform a variety of supernatural feats (such astelekinesis, clairvoyance, precognition, and mind control) and also can amplify certain physical traits, such as speed and reflexes; these abilities vary between characters and can be improved through training.

While the Force can be used for good, it has a dark side that, when pursued, imbues users with hatred, aggression, and malevolence.