Visible Light

3.3 Visible Light

2 Cor 3:18

Types of Objects

• Luminous objects: Give off their own light.

• Illuminated objects: Visible because they are lit up.

Incandescent

• Production: Filament heated until it glows.

• Light comes from heat.

• Temperature: Hot.

• Cost of bulb: $

• Power use: High.

Fluorescent (CFL)

• Production:

  • Electrons bombard gas (mercury vapor plus argon, xenon, or neon).

  • Gas is excited and produces UV.

  • Phosphors absorb UV and produce visible light.

• Temperature: Cool.

• Cost of bulb: $</p></li><li><p><strong>Power use:</strong> Low (13 watts).</p></li></ul><h4 id="878e4faa-5886-45e0-bf7d-6bd8b1079e6e" data-toc-id="878e4faa-5886-45e0-bf7d-6bd8b1079e6e" collapsed="false" seolevelmigrated="true">Neon</h4><ul><li><p><strong>Production:</strong></p><ul><li><p>Electrons bombard neon gas.</p></li><li><p>Gas produces red light (different colors with different gases).</p></li></ul></li><li><p><strong>Temperature:</strong> Cool.</p></li><li><p><strong>Cost of bulb:</strong>$$

• Power use: Low.

LED

• Production:

  • Current goes through a semiconductor.

  • Semiconductor produces light.

  • Different semiconductors produce different colors.

  • Heat destroys the crystal, so a heat sink allows it to cool.

• Temperature: Cool.

• Cost of bulb: $$$

• Power use: Very low (6 watts).

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