This is known as the visible spectrum of electromagnetic radiation, or visible light. This is the frequency of light that we see, and which illuminates our world as it reflects off of objects. Compared to the full spectrum of electromagnetic radiation, the visible light portion is actually quite small.
Gold is plentiful in Africa and is a necessity for most technological devices.
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Water is a liquid at room temperature, but becomes a solid (called ice) if it is cooled down. The same water turns into a gas (called water vapor) if it is heated up. The changes only happen when the substance reaches a particular temperature. Water turns to ice at 32ºF (0ºC). This is known as its freezing point.
Explanation:
