Law of refraction i) The incident ray, refracted ray and the pt of incident all lie in the same plane. (Explain graphically) ii) ratio of Sine<i to the Sine<r is equal to the constant 'n' i.e., refractive index. (explain abt this constant, why it has been introduced) why "Sine" is used here, why not "cosine" or "tangent"
If the questin is why the sine wave was introduced, I may be able to answer that if you can tell me who introduced it ! Personally I'd have done for a square wave more digital type of thing ya know... Google a bit will you, many of us a done it already, your turn to do research a some.
Light doesn't come in square waves. Not even if one pays extra. Snell's law uses the sine because the sine works. Snell came up with his equation by observing nature, not designing it.
i) The incident ray, refracted ray and the pt of incident all lie in the same plane. (Explain graphically) Thanx i got the exact ans for the 2nd point but plz explain the above one
Secondly how the "Normal" is drawn in the prism i think its related with both the incident ray and refracted ray but my q is tht whether we first draw normal or incident ray n refr ray
They all lie in the same plane because light travels in straight lines and not curved trajectories. At least in the absence of strong gravitational fields such as would be found in the vicinity of a Black Hole. The refractive index is introduced so the path of a refracted beam may be computed. It uses the sine function because the geometry requires it. Where did you get the quaint notion that various trigonometric functions were somehow equivalent and interchangeable?
"Normal" is a gemetry term. It means "at right angles to the plane." Draw it whenever you like, as long as you remember to draw it perpendicular to the surface. I'm not sure what is meant by "graphic explanation." The incident and reflected (or refracted) rays share a common point. Any two intersecting lines (or rays) are co-planar. This is because of the definition of "line" and "plane." The common point (the point of reflection or refraction) and any other point along the ray define the ray. The common point, along with the two random points defining the two rays, define a plane.