COMPOUND MICROSCOPE

INTRODUCTION

Compound microscopy is an important tool in many sectors, including science, research, medical diagnostics, medicine, engineering, and education.  A compound microscope is built using a mix of lenses and other optical components.Let us go through the concept, lens combination, operating, and magnifying power of the lenses.

COMPOUND MICROSCOPE – IMAGE FORMATION

CONSTRUCTION

There are two lenses  combined in a compound microscope which allows much higher magnification. The compound microscope consists of a long cylindrical tube in which one end of the tube has an objective lens (small aperture and small focal length)  and the other end has an eyepiece lens (the aperture and the focal length are somewhat larger than the objective lens).

Objective lens which focuses a real image of the object,the image is further magnified by the  eyepiece which gives the viewer an image  that is virtual, magnified and inverted concerning the object(AB).

COMPOUND MICROSCOPE-IMAGE

WORKING

The object (AB) which is to be magnified is placed between the F and 2F of  the objective lens(close to F) in order to get an image (A’B’) of real,inverted and magnified, that is beyond 2F on the other side of the objective lens. (see the image).

The image A’B’ produced by the objective lens acts as an object for the second lens (eyepiece) .The eyepiece  is adjusted so that the object( image of objective lens) lies between  the principal focus and the optic center of the eyepiece lens. (see the second right side image, simple microscope principle).

The image yielded by the eyepiece (A »B »)  is virtual, magnified and inverted concerning the object (AB).

MAGNIFYING POWER

SIMPLE MICROSCOPE – PRINCIPLE

COMPOUND MICROSCOPE- NUMERICAL

NUMERICAL-1

The objective lens and the eyepiece used in a compound microscope are of focal lengths 4 cm and 10 cm respectively. An object is placed at a distance of 6 cm from the objective lens. What will be the magnifying power and length of the compound microscope?

SOLUTION

NUMERICAL -2

The objective lens and the eyepiece  used in a compound microscope are of focal lengths 2 cm and 3 cm respectively.The distance between objective  lens and the eyepiece lens  is 15 cm. The final image is formed at infinity.What is the distance of the object and image produced by the objective from the objective lens?

SOLUTION

REFRACTION THROUGH A PRISM

REFRACTION THROUGH A PRISM – IMAGE

REFRACTION THROUGH A PRISM- DESCRIPTION

REFRACTION THROUGH A GLASS SLAB

REFRACTION THROUGH A GLASS SLAB – IMAGE

REFRACTION THROUGH A GLASS SLAB – DESCRIPTION

CONVEX LENS SIGN CONVENTION

CONVEX LENS SIGN CONVENTION- IMAGE

CONCAVE MIRROR SIGN CONVENTION

CONCAVE MIRROR SIGN CONVENTION-IMAGE

ANGLE OF MINIMUM DEVIATION

REFRACTION OF LIGHT

TOTAL INTERNAL REFLECTION

DISPERSION OF WHITE LIGHT

Dispersion of light is due to the spatial separation of white light into components of different wavelengths(different colors).Simply, the phenomenon of splitting  of white light into components of different colors on passing through a refracting medium.

Dispersion is  the  change in the angle of refraction of  different colors of light. Dispersion occurs in a medium when different wavelengths/frequencies travel at different speeds.

DISPERSION OF LIGHT-IMAGE

SPEED OF LIGHT IN A MEDIUM (v)

VISIBLE LIGHT AND VISIBLE SPECTRUM

_{OPTICAL DENSITY}

Glass prism has a higher optical density than air. Optical density is the measure of the tendency of the material to slow down the light. Light waves through the material interact with the atoms.

The refractive index of the medium is caused by the atoms absorbing the light and after a time they re-emit the light. The process of absorption and re-emission is repeated. This causes the path of the ray to bend or deviate from the original path.

CAUSE OF DISPERSION

The refractive index of the refracting medium is different for different wavelengths.

CAUCHY’S EQUATION: This equation gives the relationship between refractive index and wavelength of light for a particular transparent material.

EXAMPLE OF DISPERSION

An example of dispersion is the formation of a rainbow.It is the phenomenon caused by dispersion,refraction, and total internal reflection of light in water droplets that lead to the formation of a spectrum of light in the sky.Raindrops in the atmosphere act like small tiny prisms.

Diffraction grating is an optical component which  splits and diffracts the light into several beams.

DIFFRACTION DUE TO SINGLE SLIT

INTERFERENCE OF LIGHT

Destructive interference

Constructive interference