Question

There a 90 degree configuration between the exciting beam and the optics of collecting fluoresecence in a real spectrofluorometer

1. what do we most likely see when the detector is placed at 180 degrees ( as we do in an absorption spectrophotometer)?

*please no cursive hand writing, please use normal block script / printed hand writing

Answer 1

In this spectroflourometer we generally place the detector at 90° to the incident light beam to reduce the risk of transmitted or reflected incident beam to reach the detector. Various light source may be used as excitation source for flouremeter(Spectroflourometer). As we need beam of different wavelenghts so we use monochromater or filters in flourimeter that allows adjustable wavelength with adjusted tolerance. The most common filter utilizes the diffraction gratings, that is , a collimated beam of light illuminates the grating and exits with different angle according to wavelength needed. As mentioned above flourescence is often measured at 90° angle relative to excitation beam but also this apparatus geometry is also used when detector is placed at angle of 180°. This will help us to avoid the interference of transmitted excitation light beam. For the  case of 180° placement of detector we get reduced signal-to-noise ratio and a better detection limit as compared to 90° geometry. So this has both pros and cons of changing the geometry.

Image is attached for a simple flourimeter.