Hotter objects: the glow shifts toward blue
A blacksmith heats an iron bar. It glows dull red, then orange, then white as it gets hotter. The color tracks the temperature.
A hotter object emits more each second. Heating changes a second thing as well: where on the spectrum the emission is strongest.
An object's emission is spread over many wavelengths, stronger at some than at others.
The wavelength where its emission is strongest is called its peak.
A warm bar's emission peaks at long wavelengths, outside the visible band.
Heating an object further shifts the peak of its emitted radiation toward shorter wavelengths and greater frequencies.
Heated further, the peak shifts toward shorter wavelengths and greater frequencies.
A barely warm bar's peak sits far into the long wavelengths, well outside the visible band.
As the bar heats, its peak moves toward shorter wavelengths, and the glow the eye sees turns dull red, then orange, then white.
The iron bar's story on the scale: each hotter stage moves the peak another step toward the short-wavelength end.
Cooling runs the shift backward: the peak moves toward longer wavelengths and lower frequencies.
Hotter always reads the same way on the spectrum: peak toward the short-wavelength, high-frequency end.
One star glows reddish; another glows bluish white. Which is hotter?
A hotter emitter's peak sits at shorter wavelengths.
Blue sits at the short-wavelength side of the visible band; red at the long side.
The bluish white star is hotter.
An oven element is switched off and cools. Which way does its emission peak move?
Cooling is the heating trend in reverse.
The peak moves toward longer wavelengths and lower frequencies.
Toward longer wavelengths.
An object is heated further and further. Which way does the peak of its emitted radiation shift?
Two filament lamps run side by side, and one filament is hotter. Which statement is correct?
Xander says: 'Heating an object further shifts its strongest emission toward greater frequencies.' Is Xander correct?
Your turn
Which statement describes what further heating does to an object's emitted radiation?
Object A's emission peaks in the infrared; object B's emission peaks in the visible band. Which statement is correct?
A bar glowing white is left to cool: white, then orange, then dull red, then no glow. What is its emission peak doing?