Take a blowtorch (figuratively!) and heat up an iron bar. After a moment it will glow red, then orange, then bluish-white. Then it’ll melt. ...Yes... why indeed?
Why does it glow? Any matter above the temperature of absolute zero (about -273 Celsius) will emit light. The amount of light it gives off, and more importantly the wavelength of that light, depends on the temperature. The warmer the object, the shorter the wavelength.
...
An object that is at 4500 Kelvins (about 4200 Celsius or 7600 F) peaks in the orange part of the spectrum. Warm it up to 6000 Kelvin (about the temperature of the Sun, 5700 C or 10,000 F) and it peaks in the blue-green. Heat it up more, and the peaks moves into the blue, or even toward shorter wavelengths. In fact, the hottest stars put out most of their light in the ultraviolet, at shorter wavelengths than we can see with our eyes.
Now wait a sec (again)… if the Sun peaks in the blue-green, why doesn’t it look blue-green?
Phil tells us why.
No comments:
Post a Comment