Vision and Perception Flashcards
Rods
extremely sensitive to low levels of light and do not detect color
Cones
the receptors used to see under bright conditions, give us the ability to sense color and resolve fine detail in what we see in three types: red, blue, and green light
Perception
Your brain must take the electrical information from the optic nerve and convert it into information that you can use
The Visual Field (4)
- each eye’s: 135 degrees high and 160 degrees wide
- both eyes is 200 degrees
- includes peripheral vision
- we use approximately a 60-degree angle
Light Waves
light is made of waves of energy
visible light spectrum (2)
- Only a small section of the electromagnetic spectrum is visible to the human eye
- typical human eye will respond to wavelengths from about 400 to 700 nanometers
gamma rays
shortest wavelengths of 10-6 nanometers
color (4)
- frequency of a light wave determines its color.
- Green is at the center of the visible light color spectrum
- Blue light waves have a higher frequency
- Red light waves have a lower frequency
amplitude
determines the intensity of the light
Light and the Inverse Square Law
a specified physical quantity or intensity is inversely proportional to the square of the distance from the source of that physical quantity
Direct light measurement (3)
- Lumem
- Lux
- Foot-Candle
Lumen
a measure of the light quantity emitted from a constant light source across one square meter.
Lux
a contraction of the words luminance and flux; 10.7 lux is equal to 1 footcandle
Foot-Candle
an English unit of measurement expressing the intensity of light illuminating an object. The illumination from one candle falling on a surface of 1 square foot at a distance of 1 foot
Footlambert
a U.S. customary unit of measurement for luminance. It is equal to 1/pi candela per square foot
Candela
replaced the candlepower standard
Behavior of Light (5)
- Refraction
- Dispersion
- Reflection
- Scattering
- Absorption
Refraction
Refraction is the bending or changing of the direction of a light ray when passing through a material, such as water or glass. How much light refracts, meaning how great the angle of refraction, is called the refractive index.
Dispersion
can be seen when a white light beam passes through a triangular prism. The different wavelengths of light refract at different angles, dispersing the light into its individual components.
Reflection
light or sound energy that has been redirected by a surface
Scattering
occurs when light hits a textured surface, the incoming light waves get reflected in multiple angles because the surface is uneven.
Absorption
Light being consumed when hitting darker colors
Inverse Square Law and Light (3)
- as you move farther away from a light source the brightness of the light at the viewing point will diminish
- As the distance from the light source is doubled, the perceived illumination decreases by 75 percent
- The illuminance of a surface varies inversely as the square of its distance from a light source
Inverse Square Law Quick Tip
- As distance is doubled, the illumination of light is quartered
- As distance is doubled, the surface area of light quadrupled
