Why do we set the spectrophotometer or colorimeter to a wavelength of 565 nm or ""green"" in order to measure the absorbance of crystal violet?

Hey can you me with this i really need y’all

Which of the following changes will decrease the total amount of gaseous solute able to be dissolved in a liter of liquid water? (2 points) decreasing temperature decreasing pressure decreasing surface area decreasing solute concentration

Which is an example of a reversible physical change?