Which is brightest metal?

I’ll give you the short, and mildly incorrect, answer first:

Silver is the brightest metal.

Silver has been revered for thousands of years for its brightness. It is used to make the finest mirrors, though it must be covered with glass because it tarnishes quickly in the presence of oxygen.

For a slightly longer answer…

By “brightest,” you’re likely asking which metal reflects the most visible light. This is measured scientifically through a property called Reflectance.

Reflectance measures the effectiveness of a material of reflecting radiant energy. As you might know, radiant energy exists on a broad spectrum, only a tiiiiiiiiny portion of which is visible.

This area, between about 390 nanometers and 700–750 nm, is known as the visible spectrum.

I bring this up because the Reflectance of a material depends upon the wavelength of the energy it’s reflecting. By looking at this chart on the Reflenctance of Gold (Au), Silver (Ag) and Aluminum (Al), you can determine that:

• Gold and Silver are poor reflectors of ultraviolet energy; Aluminum is much better.
• Within the visible spectrum (390–750), Gold is a poor reflector of violets, but it is the best reflector from about 600–800 nm, meaning it reflects oranges and reds the best.
• In the violet area, Aluminum is much better than the other two metals, but in the orange-to-red area, it is the worst of the three.
• All three metals are excellent reflectors of infrared energy.
• Silver is better than Aluminum from green all the way through red.

So, you see, given that:

1. By “brightest,” you most likely mean “most reflective of visible light”

2. Materials have different Reflectance at different wavelengths

You must conclude that the “brightest” material depends upon what color of light you’re shining on it. If you’re shining red light on it, Gold is the best. If you’re shining violet light on it, Aluminum is the best. For sunlight, which contains all of the constituent colors, Silver is most likely the best overall.

Incidentally, gold’s poor reflectance of violet and blue is what accounts for its yellow color. Aluminum and silver are pretty consistent over the visible spectrum, which is why they look whitish.

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