Introduction to microscopes:

Concept of Resolution:

• The image of an object can be magnified when viewed through a simple lens. By combining a number of lenses in a suitable manner, a microscope can be produced. This would yield very high magnification values.

• Resolving the smallest distance between two points, basically, referred as resolution or resolving power (Eye resolution: 0.1 ~ 0.2 mm).

• The instrument revealing details finer than 0.1 mm → Microscope.

• The Rayleigh criterion defines the resolution of a light microscope as:

• δ =0.61*[λ/( μ .sinβ )]

• where λ is the wavelength of the radiation, μ is the refractive index of the view medium and β is the semi-angle of collection of the magnifying lens.

• Taking green light as an example (λ = 550 nm), the typical resolution value turns out to be → 300 nm.

Quiz 9:

(Q9.1). Why do we need a microscope?

(Q9.2). Who found microscope?

(Q9.3). How does a microscope work?

(Q9.4). What is the best resolution one can obtain by an optical microscope?

(Q9.5). Is there any limitation on the number of lenses to build a microscope? Why?