Red, green, and blue are the primary colors of light—they can be combined in different proportions to make all other colors. For example, red light and green light added together are seen as yellow light.

Primary sources can either be first-hand observation/analysis. Primary sources document events, people, viewpoints of the time. Primary sources represent one person’s perspective; A primary source that the researcher be cognizant of and sensitive to the bias of the observer/analyzer that created the primary source.

Primary sources can either be first-hand observation/analysis, or accounts contemporary with the events described. Primary sources document events, people, viewpoints of the time. When research is more era, rather than event driven, scope of possible primary sources broadens considerably.

Primary Data: They are deliberately, rigorously, and consciously collected from the relevant respondents to generate original information that can be used directly to solve the marketing problem. They are collected as per company’s plan.

Primary data is a type of data that is collected by researchers directly from main sources through interviews, surveys, experiments, etc. For example, when doing a market survey, the goal of the survey and the sample population need to be identified first.

A light source is anything that makes light. There are natural and artificial light sources. A few examples of natural light sources include the Sun, stars and candles. A few examples of artificial light sources include light bulbs, lamp posts and televisions.

The primary properties of visible light are intensity, propagation-direction, frequency or wavelength spectrum and polarization, while its speed in a vacuum, m/s, is one of the fundamental constants of nature.