Explain why microscopes of high magnifying power have oil-immersion ob

1.	Explain why microscopes of high magnifying power have oil-immersion objectives.
Answer» a. To avoid obscuration of details of micro-objects by diffraction effects, microscope of high magnifying power must have high resolving power. b. R.P. of microscope \(=\frac{2\mu\,sin\,\alpha}{\lambda},\) where μsinα is termed as numerical aperture. Thus, R.P. ∝ μsinα c. To increase α, the diameter of objective would have to be increased. This would degrade image by decreasing resolving power. d. Oil has higher refractive index (μ_oil > μ_air) hence to increase resolving power of microscopes of high magnifying power, the object is immersed in oil that is in contact with objective. e. Usually cedar oil having refractive index 1.5, close to that of the objective glass is used.

Explain why microscopes of high magnifying power have oil-immersion objectives.

Answer»

a. To avoid obscuration of details of micro-objects by diffraction effects, microscope of high magnifying power must have high resolving power.

b. R.P. of microscope \(=\frac{2\mu\,sin\,\alpha}{\lambda},\) where μsinα is termed as numerical aperture.

Thus, R.P. ∝ μsinα

c. To increase α, the diameter of objective would have to be increased. This would degrade image by decreasing resolving power.

d. Oil has higher refractive index (μ_oil > μ_air) hence to increase resolving power of microscopes of high magnifying power, the object is immersed in oil that is in contact with objective.

e. Usually cedar oil having refractive index 1.5, close to that of the objective glass is used.

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