WAVE OPTICS

1.  1. Diffraction Pattern

The non-uniform distribution of light energy obtained on the screen due to bending of lights rays at the corners or edges of the slit is called diffraction pattern.

2. Diffraction

The bending of light rays around the edges and corners of the obstacles is called diffraction.

3. Width of central maximum:- The width of central maximum is the linear distance between the first minima on the either side of central maxima of the diffraction pattern.

4. Fresnel’s distance the distance of screen from the slit at which the spreading of light becomes just equal to the size of the slit is called Fresnel’s distance.

                                                D_f=a²/lemda

There are two classes of diffraction

1.  Fresnel diffraction

2.  Fraunhofer diffraction

the diffraction pattern is due to a single rectangular slit consists of broad and intense central maximum and a number of narrower and fainter maxi-ma called secondary maxi-ma on the sides of central maxi ma. The width of central maximum is twice the width of fainter side maxi-ma.

5. An arrangement consisting of a large no. of equidistant narrow parallel rectangular slits of equal width separated by equal opaque portions called a diffraction grating.

6. The ratio of the change in angle of diffraction of any two neighboring spectral lines to their change in wavelength is called dispersive power.

7. Prism diffraction is due to refraction. Grating spectra is due to diffraction. Prism spectra has only one order and hence brighter. Grating spectra has different orders and so light is distributed to different orders.

8. Polarization tells us about the transverse nature of light waves.

9. The phenomenon in which light vibrations are confined to a single plane is called polarization of light.

10. Plane polarized light can be produced by reflection, refraction, and scattering.

11. Brewster’s law: the tangent of the angle of polarization for a given medium is numerically equal to the refractive index of medium. The angle at which the refracted ray from a transparent medium is plane polarized is called polarizing medium.

12. Pile of plates is used to produce polarized light by refraction.

13. Malus law: Malus law stated that when a completely plane polarized light is incident on a polarizing sheet the intensity of light transmitted through the analyzer varies as the square of cosine of the angle between the plane of transmission of the analyzer and the plane of polarizer.

14. When a light rays is passed through calcite or quartz crystal we get two defracted rays .one refracted rays obeys the laws of reflection and is called the ordinary ray or O-ray. The other ray does not obey the laws of refraction and is called the extraordinary ray or E-ray.

15. When a beam of unpolarised light is passed through certain       crystal like tourmaline , the light splits up into two beams,  polarized at right angles to each other; the light with vibrations perpendicular to optic axis are absorbed and the other components with vibrations parallel to the optic axis is transmitted. The selective absorption is called dichroism and the crystal are said to be diachronic.

16. Polaroid work on the principal of dichroism.

17. Polaroid are made by embedding the tiny synthetic crystals of harapathitewith their optical axis parallel in the transparent film of cellulose acetate.

18. Polaroid are used, in motor car head lights , in sunglasses, to view 3d pictures, as filters in photographic camera.

ATOMS

ATOMS

The conclusion drawn from the alpha particle scattering experiments are

The positive charge of the atom is concentrated in a small core called the nucleus.

The whole mass of the atom remains in a small region of atom and the space around the nucleus is almost empty.

The shortest distance between the alpha particle and nucleus, when the kinetic energy of alpha particles becomes equal to the potential energy of alpha particle-nucleus system, is called the distance of closest approach of alpha particle during a head on collision.

Drawback of Rutherford atom model are, he could not explain the stability of atoms and origin of line spectrum.

According to Bohr, the angular momentum of the electrons is an integral multiple of h/2π. An electron does not radiate energy when it is in stationary orbit. Electrons radiate energy when the electron jumped from permitted high energy orbit to the lower energy orbit.

The difference between the energies between two states is radiated as a photon of energy hv.

The innermost orbit with n=1 is called the ground state. Other energy levels with n=1,2,3,… are called exited states.

The spectrum of light emitted by sun is called this solar spectrum and is found to be crossed by a large no. of dark and fine lines.

The energy required to raise an atom from its normal state to the exited state is called the excitation potential of the atom.

The ionization potential of an atom is the energy required to remove an electron from the ground state to an infinite distance from the nucleus.

The various quantum numbers needed to specify the state of an atom are 1.  The principal quantum number  2.the orbital quantum no. 3. Magnetic orbital quantum number  4.spin quantum no.

Pauli’s exclusion principle states that “no two electrons in an isolated atom can have the same values for all quantum numbers”.

X- Rays are electromagnetic waves having wavelength from 0.5 A 15A. X-Rays of long wavelength are called soft x-rays and that of short wavelength are called hard x-rays.

x-rays are produced when fast moving electrons are suddenly stopped by a target.

The intensity of x rays depend on the number of electrons further depend on the filament current.

The quality of x rays depend upon its penetrating power depend on the p.d. across the tube.

X rays are electromagnetic waves. They are not deflected in electric or magnetic field. The affect photographic plate. They can penetrate matter.

Moseley’s law states that the frequency of the spectral line in a x ray spectrum varies as the square of atomic number of the elements emitting it.

ADSORPTION(CHEMISTRY)

Absorption : It is a phenomena in which a substance is uniformly distributed all over the surface.

Adsorption : the existence of a substance at a surface in different concentration than in the adjoining bulk is called adsorption. It is a selective adsorption.

Types of adsorption: Depending upon the nature of forces between the molecules of adsorbate and the adsorbent, the adsorption may be classified as:

1.   Physisorption

2.   Chemisorption

Freundlich adsorption isotherm: the adsorption of a gas on the surface of solid depends upon the pressure of gas. The extent of adsorption is generally expressed as x/m, where m is the mass of adsorbent and x is the mass of adsorbate when equilibrium has been attained. On the basis of experimental studies, Freundlich established the following relationship between the amount of gas adsorbed (x) per unit mass of adsorbate (m) and the pressure (p).

                                      x/m =kp^1/n

Where n is a constant
(whole number)which depends upon the nature of adsorbate and adsorbent.

Factor affecting the adsoption of gases on solids :

1.   Nature of gas : the easily liquefiable gases like NH₃, HCL, CO₂, etc. are adsorbed to the great extent then the permanent gases such as H₂, O₂, N₂< etc.

2.   Nature of adsorbent : activated charcoal is the most common  adsorbent for the gases. The gases such as H₂, O₂, N₂, are adsorbed on the metal Ni, Pd, etc.

3.