Instructional Objectives : Instructional Objectives Pupil will be able to understand the concept of refraction.
Pupil will be able to understand the cause of refraction.
Pupil will be able to define laws of refraction
Pupil will be able to define the refractive index.
What I expect from you to know : What I expect from you to know Pupil should have knowledge of light.
Pupil should have knowledge of speed, wave length.
Pupil should have basic knowledge of angles and basic mathematical operations.
Refraction of Light : Refraction of Light The phenomenon of bending of light when it passes from one medium to another is called refraction.
The refraction occurs at the boundary of separation of two medium.
Factor on which the bending of light depends : Factor on which the bending of light depends The direction of bending of light depends upon optical density of both media.
When light travel from rarer to denser medium it bends towards normal.
When light travel from denser to rare medium it bends away from normal.
Refraction does not take place if light incident through normal.
Cause of refraction : Cause of refraction refraction occurs as light passes across the boundary between two medium. Refraction is merely one of several possible boundary behaviors by which a light wave could behave when it encounters a new medium or an obstacle in its path. The transmission of light across a boundary between two media is accompanied by a change in both the speed and wavelength of the wave. The light wave not only changes directions at the boundary, it also speeds up or slows down and transforms into a wave with a larger or a shorter wavelength
Slide 6 :
Laws of refraction : Laws of refraction The incident ray ,the refracted ray and normal at the point of incidence lie in the same plane.
The ratio of the size of the angle of incidence to the size of angle of refraction is a constant for a given pair of media.
sin i/sin r=n ( n is known as refractive index of IInd medium w.r.t. Ist medium.
Also
n=C/Vmedium
Applications of Refraction : Applications of Refraction
Slide 9 :
Testing understanding : Testing understanding Q.1.Refraction is a surface/boundary surface phenomenon?(T,F.)
Q2.When light goes from denser to rarer medium it bends towards normal?(T,F)
Q3.Refraction takes place when light incident from normal.(Y/N).
Q4 A stick immersed in water appears bent and short when viewed from above(Y/N)
Q5.Twinkling of stars is due to refraction of light(T/F).