# RAY OPTICS PDF

The path is called a ray of light, and a bundle of such rays constitutes In the field of optics, Newton – the experimenter, was greater than Newton – the theorist . about one of the two main divisions of basic optics—geometrical (ray) optics. . Before we look more closely at the use of light rays in geometrical optics, we. Fermat's principle (=principle of least time). Optical rays traveling between A and B folIow a path such that the time of travel between the two points is an.

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weinratgeber.info - Free download as PDF File .pdf), Text File .txt) or read online for free. Ray Optics. 2. Wave Optics. ▫ We have seen that light is the wigglings of the electromagnetic field. ▫ Light behaves like a wave. Light - Geometric Optics. A. Karle. Physics Nov. 20, Chapter • Nature of light. • Reflection. • Refraction. • Dispersion. • Total internal reflection.

The heights measured upwards from principal axis are positive and downwards negative.

If m is positive then the image is virtual and erect. If m is negative then the image is real and inverted. The incident ray, normal and refracted ray all lie in the same plane.

The ratio of sine of angle of incidence and sine of angle of refraction is constant for a given pair of media. The light must propagate from optically denser medium to optically rarer medium.

The angle of incidence in the denser medium must be greater than critical angle of incidence for the given pair of media. This phenomenon is called Total internal reflection.

The field of soft x-ray astonomy was covered by P. Sanford of University College London and a colleague.

## X-ray optics

Parameters of various x-ray telescopes, either in use or to be constructed, put the case for the existence of x-ray observatories. Vickery wound up the meeting by introducing the audience to Astron Developments, formed from lontech, but shortly to have its own facilities. The company, in conjunction with the NPL and the UK National Research Development Council, had worked on a solar telescope for the European Space Agency, and performed a range of optical research, development and testing functions.

Four papers, broadly speaking two in each category, were presented after an introductory review of the subject. Atmospheric absorption and photochemistry were discussed briefly and the various scattering phenomena were reviewed.

Mention of contentious issues such as atmospheric pollution, the importance of the ozone layer and the COz greenhouse effect, and their various, conflicting effects on our climate passed unchallenged.

## ray-optics.pdf

The first main paper of the session was given by F. The minimum distance between the object and the real image in the case of a convex lens is 4f. Refraction at curved surfaces:. R is positive, if object faces convex surface R is negative, if object faces concave surface v is positive, if image is real forms on the other side of the lens v is negative, if image is virtual form on the same side of the lens First principal focus is the object point for which image point lies at infinity.

Second principal focus is the image point for which object point lies at infinity. This formula is applicable for thin lens and for paraxial rays. The focal length of a plane glass plate is infinity.

The reciprocal of focal length of a lens measured in metres is called its focal power P. The unit of focal power is dioptre. One dioptre is the focal power of a lens of focal length one metre. If a double convex lens is vertically cut into two pieces, each piece will have a focal length equal to twice the original. If a convex lens of focal length f is broken into two semicircular pieces, each piece will have a focal length f.

An air bubble in water behaves like a divergent lens i. The focal power decreases by a factor 4.

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If a glass lens is immersed in a liquid of the same refractive index, it disappears and does not act like a lens. A convex lens immersed in a liquid of refractive index greater than the refractive index of the lens behaves like a concave lens.

If a planoconvex lens of radius of curvature R and of focal length f is silvered on the plane surface, it acts like a concave mirror of focal length f R. If a planoconcave lens of radius of curvature R and of focal length f is silvered on the plane surface, it acts like a convex mirror of focal length.

Chromatic aberration: This defect is called as chromatic aberration. Characteristics of chromatic aberration: Elimination of chromatic aberration: The combination of lenses in contact with each other which minimizes the chromatic aberration is called an achromatic doublet.

The combination of a convex lens made of crown and a plano-concave lens made of flint glass acts as achromatic doublet and minimizes the chromatic aberration.

The combination of fluorite convex lens and a plano-concave lens made of flint glass is called apochromate and it removes completely the chromatic aberration. Two thin lenses made of the same material separated by a distance equal to the mean of their focal lengths eliminates the chromatic aberration. An achromatic doublet is the combination of a bi-convex lens usually crown glass and a plano-concave lens usually flint glass kept in contact.

Negative sign shows that one of the lens is concave.

Spherical aberration: Therefore the marginal rays are focuses nearer than paraxial rays. So the image formed by the marginal rays is nearer than the image formed by paraxial rays. Characteristics of spherical aberration: Elimination of spherical aberration: By using Stops: An annular disc made with opaque material acts as stop.

When it is placed in the path of the emergent rays or the central portion of the lens is obscured by a stop allowing only the peripheral rays to form the image. It allows paraxial rays by stopping marginal rays. In this method, the intensity of image will decrease. Bending of a lens: Such a lens which produced equal deviations at the two surfaces is called a crossed lens. The shape of the lens is modified to minimise the spherical aberration.

This process is called.

R1 and R2 are the radii of curvature of the lens. This factor measures the symmetry of the shape of the lens. The bending of a lens is to find that shape of the lens for which spherical aberration is minimum.

To determine the proper shape of the lens of material of index of refraction 1. Ray Optics The general rule to minimise the spherical aberration in a plano-convex lens is that the convex side should face the incident or emergent beam which ever is more parallel to the axis.

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By using plano-convex lenses: The convex surfaces of the lenses must be towards the incident rays. Suitable combination of a concave and convex lenses: For every spherical refracting surface there will be a pair of points on the axis such that all the light rays diverging from a point converge at the other point. These points are called aplanatic points.

Spherical aberration can be eliminated completely by placing the object at one of those points. Optical Instruments: The nearest point at which an object is seen clearly by the eye is called the near point of the eye. The least distance upto which on object can be clearly seen by a naked eye is called the least distance of distant vision.

The farthest point from an eye at which and object is distinctly seen is called far point, for a normal eye it is theoretically at infinity. Visual angle: It is the angle subtended by an object at the eye. It is maximum when the object is at the least distance of distinct vision.

It is an optical instrument used to see very small objects. Simple microscope: It is a single convex lens of lesser focal length. It is also called magnifying glass or reading lens. Magnification when final image is formed at D and i.

## Class 12 Physics Revision Notes for Chapter 9 - Ray Optics and Optical Instruments

Consist of two converging lenses called objective and eye lens. Final image is magnified, virtual and inverted. Final image formed at D: Generally object is placed very near to the principal focus of the objective hence 0 LD , the length of the tube.

For large magnification of the compound microscope, both f0 and fe should be small. Astronomical Telescope Refracting Type By astronomical telescope heavenly bodies are seen. It is used to see distance object on the earth.

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It is also type of terrestrial telescope but of much smaller field of view. Ray Optics 1 Objective is a converging lens while eye lens is diverging lens. Smallest angular separations d between two distant objects, whose images are separated in the telescope is called resolving limit. The resolving power of an optical instrument is defined as the reciprocal of smallest angular separation between two neightbouring objects whose images are just distinctly formed by the instrument.

The smallest angular seperation is called the limite of resolution. Huygens eyepiece: It consists of two plano-convex lenses of focal length 3f and f separated by a distance of 2f. The focal length of the field lens is 3f and focal length of eye lens is f. Convex surfaces of both the lenses will be towards incident light.

The distance of the equivalent lens from field lens is 3f. It is a negative eyepiece, since the image due to the objective is formed behind the field lens. It is not possible to provide cross wires in this eye piece. As the cross wires should be kept at the position of the image due to the objective. Ramsdens eyepiece: So either lens can be used as field lens or eye lens. Comparision between Ramsdens and Huygens eyepices: Huygens eyepiece Ramdens eyepiece Focal plane of the eye-piece lie in between the Focal plane of the eye-piece lie in front of the two lenses.

Image formed by the objective act as virtual Image formed by the objective act as a real object for the eye-piece, hence this is called object for the eye-piece, hence this is called positive eye piece.

Provision of cross wires is not possible. Cross wires can be provided. Eliminates spherical and chromatic aberrations Minimises the defects of spherical and completely. Field of view is inferior. Field of view is greater. Cannot be used for measurement purposes.The response time reduces since the velocity of transmission is high.

The critical angle is proportional to the wavelength of the spectral line. The rising sun appears to be bigger or oval in shape when it is at the horizon due to atmospheric refraction.

V2 When a ray travels through a glass slab, it suffers displacement or lateral shift but is not deviated.