What is Phase Contrast Microscope? What are the limitations of ordinary light microscope? Who invented the phase contrast microscope? What is the working principle of phase contrast microscope? What are the optical components of phase contrast microscope? What is the importance of Annular Diaphragm and Phase Plate in phase contrast microscope? How contrast is created in phase contrast microscopy? What are the applications of phase contrast microscope? What are the limitations of phase contrast microscopy?
Phase Contrast Microscopy (Optical Components, Working Principle and Applications of Phase Contrast Microscope)
Working Principle of an Ordinary Microscope:
In an ordinary microscope, the object is viewed due to differences in colour intensities of the specimen. To create the colour intensities, the specimen is first stained with suitable dyes which will impart specific colour. In an ordinary microscope, the contrast is obtained when the light rays pass through a stained specimen because different stains absorb different amounts of light. These differential absorption properties of stained specimen modify the intensity or amplitude of the light waves transmitted by different regions of the cells and this ultimately creates contrast in the image. Thus, staining is essential to create contrast in an ordinary microscope. Moreover, the unstained specimen cannot be observed through an ordinary microscope.
The Phase Contrast Microscope is used to visualize unstained living cells. Most of the stains or staining procedures will kill the cells. Phase contrast microscopy enables the visualization of living cells and life events.
Titration Curve of a Weak Acid and its pKa (Titration, Titration Curve, Titration Curve of Acetic Acid and its Significance)
What is Titration?
Titration is a method to determine the concentration of a dissolved substance (analyte or titrand) in a known volume by reacting it with another substance of known concentration and volume (titrant). The volume of the reactants plays a crucial role in the titration and thus the titration is better called as ‘volumetric analysis’.
There are different types of titrations in which the Acid-Base Titration is the most common one. The acid-base titration is used to determine the amount (concentration) of an acid in a given solution. In an acid-base titration, a known volume of acid (of unknown concentration) is titrated against a solution of strong base (usually NaOH) of known concentration in the presence of an indicator. After the titration, the concentration of the acid in the sample is calculated using the concept N1V1 = N2V2.
N1 – Normality of the unknown acid
N2 – Normality of the known base
V1 – Volume of unknown acid
V2 – Volume of the known base
What is Titration Curve?
The titration curve is a graphical representation of a titration in which the volume of titrant is plotted on X-axis (as the independent variable) and the pH of the solution is plotted on the Y-axis (as the dependent variable).
In simple terms, the titration curve is the plot of pH of the analyte (titrand) versus the volume of the titrant added as the titration progresses.
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Proton Hopping is the process of diffusion of protons (H⁺ ions) through the network of hydrogen-bonded water molecules in the liquid water. Proton hopping is also called as Grotthuss mechanism, named after the discoverer Theodor Grotthuss. The net result of proton hopping is the fast movement of H⁺ ions in water than any other dissolved cations such as Na⁺ or K⁺. Let’s see how proton hopping occurs in water.
Water has a slight tendency of ionization. The H2O molecules can ionize into H⁺ and OH¯ ions as in the equation (1).
The ionization reaction of water can be described by its equilibrium constant. The equilibrium constant (Keq) of the ionization of water at 25°C is calculated as 1.8 X 10¯16 M. The equilibrium constant and the concentration of H⁺ and OH¯ ions formed as a result of the ionization of H2O molecules are responsible for the pH of water.