Light: Crash Course Astronomy (10:34)

In order to understand how we study the universe, we need to talk a little bit about light. Light is a form of energy.   Its wavelength tells us its energy and color.   Spectroscopy allows us to analyze those colors and determine an object’s temperature, density, spin, motion, and chemical composition. —CrashCourse

The Electromagnetic Spectrum (32:06)

Welcome to the Tour of the Electromagnetic Spectrum. This unique NASA resource on the web, in print, and with companion videos introduces electromagnetic waves, their behaviors, and how scientists visualize these data.   Each region of the spectrum is described and illustrated with engaging examples of NASA science.—NASA

Refraction and dispersion are shown as the continuous beam of white light dispersed by the transparent prism.   The beam represents the combined wavelengths of visible light, (7 here), as they travel through a black vacuum with equal speeds.   The prism causes the light to slow down, which bends its path by the process of refraction. Con't...

How We See (0 - 1:23)

The lens (10) of our eyes are transparent biconvex structures that act like prisms.   Along with the cornea (8), the aqueous humour (7) and vitreous humour (1), it refracts (bends) light, focusing it onto the retina (30).  The cornea (8) is the transparent front part of the eye that covers the iris (9), pupil (6), and anterior chamber (7) refracts light, accounting for approximately two-thirds of the eye's total optical power. —

Function of the Eye

Retina (30) Focusing light onto the retina causes chemical changes in the photosensitive cells that trigger nerve impulses which travel to the brain.   It contains two forms of photosensitive cells important to vision, rods and cones.   Though structurally and metabolically similar, their function is quite different:

The fovea (26), directly behind the lens, is a dip in the retina directly opposite the lens and consists of mostly densely-packed cone cells.   It is largely responsible for color vision in humans, and enables high acuity (detailed central vision), such as is necessary in reading or any other task which primarily requires looking at things.— Wikipedia

Visual Processing

Rod cells (in the retina - 30) are highly sensitive to light allowing them to respond in dim light and dark conditions, however, they cannot detect color.   These are the cells which allow humans and other animals to see by moonlight, or with very little available light (as in a dark room).   This is why the darker conditions become, the less color objects seem to have.

Cone cells , (in the retina - 30) conversely, need high light intensities to respond and have high visual acuity.   Different cone cells respond to different wavelengths of light, which allows an organism to see color. —Ask a Biologist at Arizona State University

A Game to Map The Brain

eyewire.org

"A team of researchers from MIT reported a new map of a neural circuit in the eye that helps detect movement."

A Game to Map The Brain

eyewire.org

"A team of researchers from MIT reported a new map of a neural circuit in the eye that helps detect movement."

Rods help us see under low-light conditions but can't help us distinguish colors.

Cones don't function well in the dark but allow us to see vibrant colors in the daylight.

"Additive" Color Model

is a structured system used in digital devices and light-based media to create a gamut of colours from a small set of primary colours—in this case, red, green, and blue.cont...— Britannica

"Subtractive" Color Model

is used by artists primarily working in paint. If all of its primary colours—red, yellow, and blue—are combined, theoretically they would create black. This is because the pigments of paint selectively absorb and reflect light to create colour. cont...— Britannica