Answer the question number 19 by an expart which i easely understand

Answer the question number 19 by an expart which i easely understand VOLTEU • 10:58 uc ear eac or WI xp aln e wor Ingo a the help of a labelled diagram. 18. Describe how a Semi-Conductor diode is used as a half wave rectifier. SECTION-C Answer any Two Questions (Long Answer Type) 2 X8=16 19. Describe the construction and working of a compound microscope with a neat diagram. Derive the expression for its magnification. 20. Describe the construction and working of a moving coil galvanometer. Obtain the relation between current and deflection of the coil. The resistance of M.C.G is 5W. The maximum current it can measure is 0.015A. How would you convert it into voltmeter to measure 1.5 volts? 21. State Bohr's Postulates. Derive the expression for the radius of the first orbit in a Hydrogen atom. Radius of the first orbit of a Hydrogen atom is 5.3 x 10-11 m. What are the radii of the n2 and n3 orbits?

Dear Student,
Ray diagram of a compound microscope.

Compound microscope: It is an optical device used to see a highly magnified image of tiny objects.  

Construction: It consists of two convex lenses of short focal length arranged co-axial at the free end of the tube, at a suitable fixed distance.  

Objective: It is a convex lens of very short focal length fand small aperture, kept near the object.

Working Principle: 

The most commonly used microscope for general purposes is the standard compound microscope. It magnifies the size of the object by a complex system of the lens arrangement.

It has a series of two lenses; (i) the objective lens close to the object to be observed and (ii) the ocular lens or eyepiece, through which the image is viewed by eye. Light from a light source (mirror or electric lamp) passes through a thin transparent object The objective lens produces a magnified ‘real image’ first image) of the object. This image is again magnified by the ocular lens (eyepiece) to obtain a magnified ‘virtual image’ (final image), which can be seen by eye through the eyepiece. As light passes directly from the source to the eye through the two lenses, the field of vision is brightly illuminated. That is why; it is a bright-field microscope.

Magnifying power: The ratio of the angle subtended by the eye by the final virtual image, to the angle subtended at the eye by the object

When the final image is formed at the least distance of distinct vision, magnifying power is,

For the image to be formed at infinity, ue = fe and

By making focal length of the objective lens small, the magnifying power can be increased.


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