Procedure for simulation
To switch the views of the equipment, click the left and right arrows on the bottom of the simulator.
- Turn on the light source.
- Choose the liquid sample.
- Water is used first to calibrate the instrument.
- Turn the refractometer scale knob to get the clear interface between the illuminated and dark regions.
- Read the index of refraction using the telescope scale.
- Temperature of the sample can be varied by using the slider.
- Repeat the experiment with different liquids and study the variation of refractive index with temperature and wavelength.
Procedure for doing real lab
Abbe's refractometer is used to measure the refractive index of the given organic liquid. Using a particular monochromatic light source, the apparatus is calibrated with water as the liquid. Adjust the micrometer screw to focus the boundary between the bright and dark regions. Adjust the refractometer scale to place the cross wire of the telescope exactly on the boundary between the bright and dark regions. Repeat the same process for different organic liquids after the equipment is calibrated.
Observations and Calculations
Refractive index of the material ‘n‘ for given temperature = ……………………
ε0 - permitivity in free space = 1.
n - refractive index of the given liquid at a particular temperature.
NA - Avogadro number = 6.023 x 10 23 mol-1.
M and ρ are the molecular mass and density of the given liquid.
For water, M - 18.01g/mol and ρ - 1000Kg/m3.
Benzene, M - 78.11 g/mol and ρ - 0.8765g/cm3.
Nitrobenzene, M - 123.06g/mol and ρ - 1.199g/cm3.
Toluene, M - 92.14g/mol and ρ - 0.8869g/mL.
Aniline, M - 93.13g/mol and ρ - 1.0217g/mL.
Ethanol, M - 46.07g/mol and ρ - 0.789g/cm3.
Example: For sodium light as source, water is the liquid the refractive index at 200C is 1.333 and polarisibility is 3.25*10-23.
1. Refractive index of the given liquid sample at a particular temperature is……………………..
2. Polarisability of the given liquid sample at a particular temperature is………………………….