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Wave Optics — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsWave Optics5 Marks
Question
Define resolving power of a compound microscope. How does the resolving power of a compound microscope change when:
  1. Refractive index of medium between the object and objective lens increases.
  2. Wavelength of radiation used is increased?
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Answer

Resolving Power of a Microscope:The resolving power of a microscope is defined as its ability to form separate images of two close objects placed near the microscope.
The minimum distance between close objects for which microscope can just form separate images of the objects is called the limit of resolution of microscope. Smaller the limit, larger the resolving power.
The angular resolving limit of microscope is $\text{d}\theta=\frac{\lambda}{2\text{n}\sin\theta},$
Where n is the refractive index of medium between object and objective.
Resolving power $\frac{1}{\text{d}\theta}=\frac{2\text{n}\sin\theta}{\lambda}$
  1. Resolving power $\alpha$ n; therefore resolving power of a compound microscope increases when refractive index (n) between the object and objective lens increases.
  2. Resolving power $\alpha \frac{1}{\lambda}$ ; therefore, resolving power of a compound microscope decreases with the increase of wavelength of light used.

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