heated gas -- emission lines
Kirchoff’s 2nd situation -- a heated gas
- gives emission lines
- wavelength’s (colors) of lines characteristic of atom (not T)
- each atom (H, He, C, N, Si, Fe, ...) has unique spectrum
- line spectrum is “fingerprint” of that atom
- Demo -- hand out gratings
- grating disperses light into it’s constituent wavelengths
- orient grating so spectra are seen to Rt. and Left of light
- ignore the second order spectrum -- further away from light
- Turn on incandescent bulb
- same spectrum as vugraph projector -- continuous spectrum from blue to red
- same source of light -- a heated solid
- “blackbody radiation”
- all heated objects emit, and the spectrum depends on the T
- without grating look at filament, 30 V dull red, 40 V becomes white (all colors present)