CBSE NOTES CLASS 12 PHYSICS
CHAPTER 10 WAVE OPTICS
Refraction of a plane wave from rarer to denser medium
Let PP’ represent the surface separating medium 1 and medium 2. Let v1 and v2 represent the speed of light in medium 1 and medium 2, respectively. Let us take a plane wave front AB, propagating in the direction A’A, incident on the interface at an angle i. If τ be the time taken by the wave front to travel the distance BC and BC = v1τ
By the time the point B on wave front travels to point C in medium 1, the point A would have travelled in medium 2, to E The new wave front will be CE and AE = v2τ.
This is Snell’s law.
If r < i then the ray bends toward the normal and the speed of the light wave in the second medium (v2) will be less than the speed of the light wave in the first medium (v1). This is correct and proves the corpuscular theory wrong.
are called refractive indices of medium 1 and 2 respectively.