Principle of Fluorescence Wavelength vs. Heat Radiation Wavelength
Fluorescence is a process where a substance absorbs light energy at a certain wavelength and then re-emits it at a longer wavelength. This phenomenon is governed by the principle of energy conservation. When a molecule absorbs light energy, it gets excited to a higher energy state. As the molecule relaxes back to its ground state, it emits light at a longer wavelength.

Energy Levels in Molecules
- When a molecule absorbs light, it promotes an electron to a higher energy level.
- The energy difference between the ground state and the excited state determines the wavelength of light emitted during fluorescence.
- This process typically results in the emission of light at a longer wavelength compared to the absorbed light.

Heat Radiation Wavelength
- Heat radiation, on the other hand, is a result of the thermal energy of molecules.
- The wavelength of heat radiation is generally shorter than that of fluorescence because it is a continuum of wavelengths emitted due to the thermal motion of molecules.

Difference in Wavelengths
- The difference in wavelengths between fluorescence and heat radiation can be attributed to the different mechanisms that govern these processes.
- While fluorescence involves the absorption and re-emission of light energy by molecules, heat radiation is a result of the random thermal motion of molecules.
In conclusion, the difference in wavelengths between fluorescence and heat radiation is a consequence of the principles of energy conservation and the different mechanisms through which these forms of radiation are emitted by molecules.