3.1. Source of Light: Natural and Artificial
3.2. Nature and Physical Properties of Light
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1. Natural and Artificial Lights Sources
a. Light sources can be either natural or artificial. Sun is the primary source of natural light, and lightbulbs or lamps are the artificial sources.
b. Light is a form of electromagnetic energy that, in the case of natural light, comes from the sun as the source and, in case of artificial light, illuminates via energy from another source.
c. No matter what the source, light has an impact on life on earth as a whole.
2. Properties of Natural Light
a. Natural light is self-generated and comes in a spectrum of colors --- the visible colors of the rays we experience.
b. The color spectrum contains light with shorter wavelengths near the violet on one end and light with higher wavelength near the red. Called ultraviolet and infrared rays respectively, these rays are not visible to us.
c. The complete spectrum of light from the natural source is ideal for plant and animal life on earth. Plants and animals thrive on natural light.
d. The darkness that follows photo activity in organisms helps rejuvenate and repair life forms at the cellular level. A moderate amount of exposure to the healthy sunlight benefits humans, as it increases one's energy and metabolism, boosts the immune system and helps build vitamin D --- all of which are essential for the body.
e. Overexposure, on the other hand, has detrimental effects on living organism. The harmful ultraviolet rays can cause conditions such as skin cancer and cataracts while also damaging the texture of the skin. For plants, the need for light and dark periods helps balance the cell activity in terms of growth and repair.
f. Sunlight is also harmful since we cannot alter or control it to suit our condition.
3. Properties of Artificial Light
a. Artificial light is man-made light generated from another energy source. Most of our activities would come to a halt if we didn't have an alternate source of light. The advantage with this light lies in the fact that we can control it at our own will.
b. We can monitor the intensity, quantity and quality of light to suit each situation.
c. Artificial light does not have as broad a spectrum of colors and wavelengths as natural light; hence, it is not as beneficial.
d. Since the light has comparatively poorer quality, its effect on plant and animal life is also not as beneficial.
e. Plants and animals exposed for prolonged periods to artificial light tend to yield poorer quality of life forms in plants and cause cellular degeneration or death in living beings.
4. Properties of Light:
Following are the properties of light that shows the behavior of light as a wave:
a. Reflection - Light is reflected off the surface like mirror such that angle of incidence is equal to angle of reflection.
b. Refraction - Refraction is the bending of light as it passes between material of different optical density
c. Dispersion - Light is composed of waves of different wavelengths that correspond to different colors of lights. When light wave passes through a material, these different wavelengths causes refraction by different amounts according to the wavelengths and which gives rise to different colors seen through prism or for rainbow.
d. Diffraction - This is the bending of light waves around obstacles in its path. ex. When a light wave comes against a barrier with a small opening, it acts as a single point source from where light emerges in all direction.
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