# Ncert 12th Physics Chapter-9

## Refracting Telescope(Astronomical)

Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Refracting Telescope(Astronomical Telescope): An astronomical telescope is an optical instrument which is used for observing distinct image of heavenly bodies like star, planets etc. Refracting telescope has two convex lenses coaxially separated by some distance. Objective is of large aperture and large focal length so that it can […]

## Compound Microscope

Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Compound Microscope: A compound microscope consists of two convex lenses coaxially separated by some distance. The lens nearer to the object is called the objective. The lens through which the final image viewed is called the eyepiece. Object is placed beyond first focus of objective which formed inverted

## Simple Microscope

Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Microscope: Microscope is an optical instrument which form large image of close and minute objects. Simple Microscope: A simple microscope is a converging lens of small focal length. When an object is at a distance less than the focal length of the lens, the image obtained in virtual,

## Dispersion By a Prism

Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Dispersion By a Prism: The phenomenon of splitting of light into its component colour is known as dispersion. The pattern of colour components of light is called the spectrum of the sunlight. When a narrow beam of Sunlight is incident on a glass prism, the emergent light is

## Prism Formula

Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Prism Formula: If the angle of incidence is increased gradually, then the angle of deviation first decreases, attains a minimum value(δm) and then again starts increasing. Note: From graph it is clear that(experimentally). 1. Angle of deviation is minimum for only one value of angle of incidence. δ→δmin,

## Prism

Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Prism: A Prism is a portion of a transparent medium bounded by two plane faces inclined to each other at suitable angle. Refraction of Light Through a Prism: Lat us consider a triangular prism ABC. Let angle of incidence and angle of refraction at first phase AB are

## Combination of Thin Lenses in Contact

Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Combination of Thin Lenses in Contact: Let two lenses A and B of focal lengths f₁ and f₂ placed in contact with each other. An object is placed at a point O beyond the focus of the first lens A. The first lens produces an image at I’

## Power of a Lens

Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Power of a Lens: The ability of a lens to converge or diverge the rays of light incident on it is called the power of the lens. The SI unit of power of lens is dioptre(D). The power of a lens is measured as the reciprocal of its

## Linear Magnification Produced by a Lens(m)

Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Linear Magnification Produced by a Lens(m): Linear magnification of a lens is defined as the ratio of the height of the image formed by the lens and height of the object. Here we will use hᵢ and h₀ with sign. Height above principal axis is positive and below

## Lens Maker’s Formula

Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics: Lens Maker’s Formula: With the help of this formula, we can design a lens of desired focal length by adjusting R₁ and R₂. Derivation: When a Ray of light from object O incident at first surface it bends towards the normal and if we extend it, then it

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