Chapter 2: Light and Vision-Slides Flashcards
The light from a primary source (like ths sun) illuminates the evironment. Generally, some of the light is reflected toward the eye, providing us with information about the environment.
Light
Light is a form of electromagnetic radiation. Light floods the environment most of them. different than sound. Light is continuously flooding the world with this form of energy.
Light doesn’t require an atmosphere. It is a field that propagates through space.
Light is mostly talked about in wavelength, not frequency.
Light travels at a constant at 168,000 miles per second. Light is instantaneous.
The wave nature of light. Light (like sound) can differ in its wavelength (frequency), phase and amplitude. Light travels much faster than soune (~186,000 miles per second in air)
Light is a form of electromagnetic Radiation. The rage of visible wavelenths of light is from about 350nm to 800 nm
Visible Spectrum
The light that reaches the eye is the product of the amount of light falling on the surfaces in the evironment (irradiance) and the fraction of light reflected from a surface (reflectance)
Examples of daylight irradiance spectra normalized at 550 nm
Light travels at a constant at 168,000 miles per second. Light is instantaneous.
Eyes
Key thing is that eyes can take information and places them using the optical system for forming information.
Formation of images by an aperture without a lens
Formation of images with a lens
The disance from a lens to the point where an image is in sharp focus depends upon the distance of light source to the lens. The closer the source the further the sharp image from the lense. Because of this fact, the shape of the human lens changes depending on the distance of the object we are looking at. This is called accomodation. For near objects, the lense becomes more curved, for distant objects, less curved.
The size of the pupil decreases as ambient light level increases. A smaller pupil helps to adjust for the light level, but also improves image quality and depth of field.
Schematic Diagram of a cross section of the human eye
Image of Retina
Cross section of the human retina. In this figure, light would reach the receptors from beow (through the other cells in the retina)
Distribution of rods and cones along a horizontal section through the retina. The receptors densities are expressed in cells per square millimeter.
Bigger cells outside the fovea are cones. Small cells in the fovea are cones. Small cells outside the fovea are rods.
What is the graph for the spectral sensitivity of rods?
Illustration of the distribution of the three types of cone photoreceptors in the human fovea. These are called the long-wavelength senseive (L), middle-wavelength sensitive (M), and short-wavelength sensitive (S) cones. Sometimes these are also referred to as the red (R), Green (G) and Blue (Blue) cones.
Spectral sensitivies of the three classes of cone photoreceptors
Neurons and Connections in the Retina
What are the two states of the Retina?
Voltage Response of Rods and Cones
Relative response of a rod photoreceptor as a function of light intensity
