Physics > Refraction of Light > 9.0 Optical instruments
Refraction of Light
1.0 Introduction
2.0 Laws of refraction
3.0 Apparent shift of an object
4.0 Thin lenses
4.1 Sign convention
4.2 Some important terms
4.3 Ray tracing
4.4 Image formed by covex lens
4.5 Image formed by concave lens
5.0 Lens makers formula & Other Functions of lens.
5.1 Thin Lens Formula
5.2 Magnification and Power of lens
5.3 Combination of lenses
5.4 Displacement method to find focal length.
5.5 Silvering of lens
6.0 Total internal reflection
7.0 Refraction through prism
8.0 Scattering of light
9.0 Optical instruments
9.1 Spectrometer
9.2 Simple microscope
9.3 Compound microscope
9.4 Astronomical telescope (Refracting type)
9.5 Terrestrial telescope
9.6 Galileo's terrestrial telescope
9.7 Reflecting type telescope
9.3 Compound microscope
4.2 Some important terms
4.3 Ray tracing
4.4 Image formed by covex lens
4.5 Image formed by concave lens
5.2 Magnification and Power of lens
5.3 Combination of lenses
5.4 Displacement method to find focal length.
5.5 Silvering of lens
9.2 Simple microscope
9.3 Compound microscope
9.4 Astronomical telescope (Refracting type)
9.5 Terrestrial telescope
9.6 Galileo's terrestrial telescope
9.7 Reflecting type telescope
It consists of two convergent lenses of short focal lengths and apertures arranged co-axially. Lens (of focal length $f_o$) facing the object is known as objective or field lens while the lens (of focal length $f_e$) facing the eye, is known as eye-piece or ocular.
The objective has a smaller aperture and smaller focal length than eye piece.
- Magnifying power of a compound microscope $$M = {m_o} \times {m_e}$$
- When the final image is formed at infinity (normal adjustment), $$M = \frac{{{v_o}}}{{{u_o}}}\left( {\frac{D}{{{f_e}}}} \right)$$
Length of tube, $L=v_o+f_e$
- When the final image is formed at least distance of distinct vision, $$M = \frac{{{v_o}}}{{{u_o}}}\left( {1 + \frac{D}{{{f_e}}}} \right)$$
where $u_o$ and $v_o$ represent the distance of object and image from the objective lens, $f_e$ is the focal length of an eye lens.
Length of the tube, $L = {v_o} + \left( {\frac{{{f_e}\,D}}{{{f_e} + D}}} \right)$
