optical properties of material......... pptx

OPTICAL PROPERTIES OF MATERIALS

1. WELCOME

2. This is a presentation on Optical properties of matter Submitted By Sudipto Kumar Biswas ID:1708012 Dept Of Chemistry Faculty Of Science HSTU Submitted To Md. Rezaul Karim Lecturer Dept Of chemistry Faculty Of Science HSTU

3. INDEX What is light? Properties of light Light and matter interaction Reflection Refraction Absorption Photo electric effect Models of photo emission from solid surface Atomic and electronic interaction

4. What is light? Light is a form of energy that travels as waves. Their wavelength determins many of the wave property. For instance, wavelength accounts for color and how it will interact with matters. The ranges of wavelength from super short to very long, is known as light spectrum.

5. Properties of light Reflection Refraction Scattering Dispersion Interference Diffraction Total Internal Reflection Polarization

6. How light interacts with matters? When light interacts with a solid, it can be reflected, absorbed, or transmitted. The amount of reflection, absorption, or transmission depends on the properties of the solid material and the wavelength of the light. For example, a material that is opaque to visible light may be transparent to infrared light. The interaction between light and solids is important in many areas of science and technology, including optics, photonics, and materials science. For example, in solar cells, light is absorbed by a solid material, generating e

7. Reflection matter can reflect light. Reflection means bouncing of light off a surface. When light strikes smooth surface, the light bounces off at an angle equal to the angle at which it hits the surfaces producing a clear image. occurs when the waves encounter a surface or other boundary that does not absorb the energy of the radiation and bounces the waves away from the surface. Law of reflection is defined as: The principle when the light rays fall on the smooth surface, the angle of reflection is equal to the angle of incidence, also the incident ray, the reflected ray, and the normal to the surface all lie in the same plane.

8. Refraction Refraction is the change of direction of light when it passes from one medium to another due to its change in speed. Light is reflected or scattered in a different direction when it interacts with a surface. The diffraction angle depends on the densities of the two mediums through which the light rays pass. Laws of refraction state that: The incident ray refracted ray, and the normal to the interface of two media at the point of incidence all lie on the same plane. The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant. This is also known as Snell’s law of refraction. The refractive index, also called the index of refraction, describes how fast light travels through the material.

9. Absorption Absorption of light occurs when light strikes a material, and the energy that it carries is absorbed by the atoms of the material and is converted into thermal energy. If the photon energy is absorbed, the energy from the photon typically manifests itself as heating the matter up. The absorption of light makes an object dark or opaque to the wavelengths or colors of the incoming wave: Wood is opaque to visible light. the frequency of the light wave matches the frequency at which electrons in the atoms of that material vibrate.

10. Photo electric effect: The photoelectric effect is the emission of electrons from a material caused by electromagnetic radiation (light). Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, solid state, and quantum chemistry to draw inferences about the properties of atoms, molecules and solids. The effect has found use in electronic devices specialized for light detection and precisely timed electron emission.

11. Experimental observation of photoelectric emission Schematic of the experiment to demonstrate the photoelectric effect. Filtered, monochromatic light of a certain wavelength strikes the emitting electrode (E) inside a vacuum tube. The collector electrode (C) is biased to a voltage VC that can be set to attract the emitted electrons, when positive, or prevent any of them from reaching the collector when negative.

12. Models of photoemission from solids The electronic properties of ordered, crystalline solids are determined by the distribution of the electronic states with respect to energy and momentum Inner photoelectric effect in the bulk of the material that is a direct optical transition between an occupied and an unoccupied electronic state. This effect is subject to quantum-mechanical selection rules for dipole transitions. The hole left behind the electron can give rise to secondary electron emission, or the so-called Auger effect, which may be visible even when the primary photoelectron does not leave the material. In molecular solids phonons are excited in this step and may be visible as satellite lines in the final electron energy Electron propagation to the surface in which some electrons may be scattered because of interactions with other constituents of the solid. Electrons that originate deeper in the solid are much more likely to suffer collisions and emerge with altered energy and momentum. Their mean-free path is a universal curve dependent on electron's energy. Electron escape through the surface barrier into free-electron-like states of the vacuum. In this step the electron loses energy in the amount of the work function of the surface, and suffers from the momentum loss in the direction perpendicular to the surface.

13. Atomic And Electronic Interaction Photoemission from atoms, molecules and solids Electrons that are bound in atoms, molecules and solids each occupy distinct states of well-defined binding energies. When light quanta deliver more than this amount of energy to an individual electron, the electron may be emitted into free space with excess (kinetic) energy that is higher than the electron's binding energy. The distribution of kinetic energies thus reflects the distribution of the binding energies of the electrons in the atomic, molecular or crystalline system: an electron emitted from the state at binding energy This distribution is one of the main characteristics of the quantum system, and can be used for further studies in quantum chemistry and quantum physics

14. Topic related questions What is light? How light interact with matter? Define reflection, refraction, absorption with examples Explain photo electric effect dtails Discribe models of photoemission from solids

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