Question

Light of wavelength 589 nm is used to view an object under a microscope. The aperture of the objective has a diameter of 0.900 cm. 

1. What do you mean by limit of resolution of an optical instrument?

2. What is the limiting of resolution of the above microscope?

3. What happens to the limit of resolution if the objective is immersed in oil? Explain.

Answer 1

1. The minimum distance between two objects at which they can be observed as separated by an optical instrument is called the limit of resolution of the instrument.

2. Limit of resolution ∆θ =

\(\frac{1.22λ}{D}=\frac{1.22\times589\times10^{-9}}{0.9\times10^{-2}}\)

= 7.98 × 10^-5 rad.

3. Decreases. Refractive index of oil is more than that of air. Hence wavelength of the light decreases.