what is meant by excitation wavelength and emission wavelength?

Answer 1

Excitation wavelength is the wavelength required for an electron to transit to a higher energy state.

Emission wavelength is the energy emitted when it comes back to the ground state.

Answer 2

The excitation wavelength is the WaveLength of the radiation (usually coming from a laser line) used to stimulate fluorescence in the measured object.

The lower the WaveLengths involved in the measurement, the higher the resolution. For a good measurement you must adapt the Sampling Density accordingly to the Nyquist Rate.

Huygens Essential will warn you if the difference between the reported Excitation Wavelength and Emission Wavelength is larger than 20%. This is just a reminder based on that many Fluoro Chromes have the difference in wavelengths inside this range. But other, as DAPI, have a larger difference. To make a proper deconvolution the correct values must be reported, despite the warning message.

The emission wavelength is the WaveLength of the radiation emitted by the object being measured, coming from the fluorescent dyes. The fluorescent emission is caused by a radiation source with a given Excitation Wavelength.

The lower the WaveLengths involved in the measurement, the higher the resolution. For a good measurement you must adapt the Sampling Density accordingly to the Nyquist Rate.

Huygens Essential will warn you if the difference between the reported Excitation Wavelength and Emission Wavelength is larger than 20%. This is just a reminder based on that many Fluoro Chromes have the difference in wavelengths inside this range. But other, as DAPI, have a larger difference. To make a proper deconvolution the correct values must be reported, despite the warning message.

Answer 3

You may have seen mineral specimens glowing various colors under excitation by ultraviolat radiation. That is one example of what you are asking about. The UV radiation is absorbed by certain molecules in the mineral, causing one or more of its electrons to jump to a higher energy level because of the absorbed UV energy. The electron then, within an extremely short time, a few milliseconds, drops back to its original position, releasing, or emitting, what remains of the UV energy it had absorbed. The full energy absorbed from the UV is no longer present because any time matter absorbs energy, some of that energy is transformed into heat, and lost. Therefore when the briefly stored energy is emitted, it is at a lower energy level than the original UV. A lower energy level means a longer wavelength, therefore the energy is released as visible light of various colors which we can see.