Question

Optical methods are used to determine​

Answer 1

Answer:

Optical methods allow the detection of density variations that occur in a fluid due to changes in temperature and/or speed and/or composition

Answer 2

Optical methods are used to detect the variations in density.

• Optical methods typically allow considerable variations in density that ordinarily occur in a ideal fluid due to necessary changes in effective temperature and/or speed and/or specific composition to be carefully observed.  
• Optical techniques are effective techniques that use light to properly investigate or adequately regulate matter.  
• Optical spectroscopy, which involves techniques such as pump-probe spectroscopy, Raman spectroscopy and photoemission spectroscopy, represents one prominent example.