IllusionAn illusion is a distortion of the senses, which can reveal how the mind normally organizes and interprets sensory stimulation. Although illusions distort the human perception of reality, they are generally shared by most people. Illusions may occur with any of the human senses, but visual illusions (optical illusions) are the best-known and understood. The emphasis on visual illusions occurs because vision often dominates the other senses.
VolunteeringVolunteering is a voluntary act of an individual or group freely giving time and labor for community service. Many volunteers are specifically trained in the areas they work, such as medicine, education, or emergency rescue. Others serve on an as-needed basis, such as in response to a natural disaster. The verb was first recorded in 1755. It was derived from the noun volunteer, in 1600, "one who offers himself for military service," from the Middle French voluntaire. In the non-military sense, the word was first recorded during the 1630s.
Optical illusionIn visual perception, an optical illusion (also called a visual illusion) is an illusion caused by the visual system and characterized by a visual percept that arguably appears to differ from reality. Illusions come in a wide variety; their categorization is difficult because the underlying cause is often not clear but a classification proposed by Richard Gregory is useful as an orientation. According to that, there are three main classes: physical, physiological, and cognitive illusions, and in each class there are four kinds: Ambiguities, distortions, paradoxes, and fictions.
Color theoryIn the visual arts, color theory is the body of practical guidance for color mixing and the visual effects of a specific color combination. Color terminology based on the color wheel and its geometry separates colors into primary color, secondary color, and tertiary color. The understanding of color theory dates to antiquity. Aristotle (d. 322 BCE) and Claudius Ptolemy (d. 168 CE) already discussed which and how colors can be produced by mixing other colors. The influence of light on color was investigated and revealed further by al-Kindi (d.
Virtual volunteeringVirtual volunteering refers to volunteer activities completed, in whole or in part, using the Internet and a home, school buildings, telecenter, or work computer or other Internet-connected device, such as a smartphone or a tablet. Virtual volunteering is also known as online volunteering, remote volunteering or e-volunteering. Contributing to free and open source software projects or editing Wikipedia are examples of virtual volunteering.
