8TH GRADE · LIGHT PHENOMENA
Sources and properties of light
Natural and artificial sources, actions and energy of light.
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Basic Concepts
Light source
A body that independently emits visible light and may be natural or artificial.
The sun and stars are natural sources, but the lamp and candle are artificial; An illuminated non-luminous body only reflects light.
Energy of light
Light carries energy and is capable of heating bodies, causing chemical reactions and biological changes.
Absorbed light energy is converted into internal or chemical energy, and its effect depends on the spectrum and intensity.
Visibility of a non-luminous body
A non-luminous body becomes visible when the light reflected or scattered by it enters the eye of the observer.
In complete darkness, an object is not visible because no light comes from it to the eye, even if the object itself is nearby.
Physical quantities
Luminous flux
A measure of the power of visible radiation taking into account the sensitivity of the human eye.
Unit: lumen ·
Tasks on the topic
Statements, answer options and the walkthrough.