Question

The diffraction effects in a microscopic specimen become important when the separation between two points is

• A. much greater than the wavelength of light used.
• B. much less than the wavelength of light used.
• C. comparable to the wavelength of light used.
• D. independent of the wavelength of light used.

Answer 1

Answer: (C)

When the wavelength of light used is comparable with the separation between two points, the image of the object will be a $\varphi$ diffraction pattern whose size will be
$\theta =\frac{1.22\lambda }{D}$
where $\lambda =$ wavelength of light used
$D=$ diameter of the objective
Two objects whose images are closer than this distance, will not be resolved.