Wave Optics class 12 physics ch 10 revision notes pdf , class 12 physics chapter 10 wave optics revision notes pdf by blue sky .
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Physical optics is also the name of an approximation commonly used in optics, electrical engineering and applied physics. In this context, it is an intermediate method between geometric optics, which ignores wave effects, and full wave electromagnetism, which is a precise theory. The word "physical" means that it is more physical than geometric or ray optics and not that it is an exact physical theory.[1]:11–13
This approximation consists of using ray optics to estimate the field on a surface and then integrating that field over the surface to calculate the transmitted or scattered field. This resembles the Born approximation, in that the details of the problem are treated as a perturbation.
In optics, it is a standard way of estimating diffraction effects. In radio, this approximation is used to estimate some effects that resemble optical effects. It models several interference, diffraction and polarization effects but not the dependence of diffraction on polarization. Since this is a high-frequency approximation, it is often more accurate in optics than for radio.
In optics, it typically consists of integrating ray-estimated field over a lens, mirror or aperture to calculate the transmitted or scattered field.
In radar scattering it usually means taking the current that would be found on a tangent plane of similar material as the current at each point on the front, i. e. the geometrically illuminated part, of a scatterer. Current on the shadowed parts is taken as zero. The approximate scattered field is then obtained by an integral over these approximate currents. This is useful for bodies with large smooth convex shapes and for lossy (low-reflection) surfaces.
The ray-optics field or current is generally not accurate near edges or shadow boundaries, unless supplemented by diffraction and creeping wave calculations.
The standard theory of physical optics has some defects in the evaluation of scattered fields, leading to decreased accuracy away from the specular direction.[2][3] An improved theory introduced in 2004 gives exact solutions to problems involving wave diffraction by conducting scatterers.
When you open your window in a room, the light enters through the window and spreads throughout the room. Do you why does this happen? This is because light has got some wave nature, that spreads in the room in all the directions. To understand this in a better way let us study the Huygen’s Principle.
Polarisation
Polarisation is nothing but transforming unpolarised light into polarised light. Unpolarised light is the light in which particles vibrate in all different planes.
( Source: Wikipedia )
Ways of Polarising the Light
Polarisation by Polaroids
( Source: s-cool )
In the above figure, we see that there is plane of vibration parrel to the plane and there is a plane of vibration perpendicular to the plane. The first image is of unpolarised one. The second image is polarised which is either perpendicular or parallel. So let us start understanding polarisation by polaroids. Polaroids are the polarising materials consisting molecules aligned in particular direction.
Every Polaroid has a pass axis. It will allow light to pass only through the pass axis. A polaroid can have horizontal pass axis as well as vertical pass axis. These determine how the light will pass through it. So when an unpolarized light passes through a polaroid, it gets polarised
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