Author name: Manoj Pandey

According to Planck’s Quantum theory, light radiations consists of tiny packets of energy called quanta. One quantity of light radiation is called a photon which travels with the speed of light. The energy of a Photon is  E= hv Where h is Planck’s Constant and v is frequency of light radiation. When a photon of energy fall

The laws of photoelectric emission are as follows (I) For a given material and a given frequency of incident radiation, the photoelectric current or number of photoelectrons ejected per second is directly proportional to the intensity of the incident light. (II) For a given material and frequency of incident radiation, situation current is found to

Photoelectric Effect: It is the phenomenon of emission of electrons from the surface of metal, when radiations of suitable frequency fall on it. Or The phenomenon of converting light energy into electrical energy is called Photoelectric effect. The emitted electrons are called photoelectrons and the current, so produced is called photoelectric current. Threshold Frequency: For

Electron Emission: In metals the electrons in the outer shells are loosely bound to the atoms, hence they are free to move easily the metal surface but I cannot leave the metal surface. Such electrons are called free electrons. These free electrons can be emitted from the metals, if they have sufficient energy to overcome

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

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

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,

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

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,