CONCEPT:
Refraction: When a ray of light passes from one medium to another it suffers a change in direction at the boundary of two media is called refraction.
- The change in direction because the speed of light travels at different speeds in different mediums.
- Refractive Index of a medium defines that it is denser or rarer
- Refractive Index = Speed of light in Vacuum /speed of light in that medium.
- Refractive Index = η = c/v where, c = Speed of light in Vacuum, v = speed of light in that medium.
Explanation:
When light passes from a region of lower n, such as air, through a surface into a region of higher n, such as glass, the light changes direction. This means its path is closer to perpendicular, or "normal," to the surface. When the light passes from a region of higher n to the region of lower n, it bends away from the "normal" direction. This is what causes the submerged part of a spoon in a glass of water to appear to bend when you put it in water.
Extra point:
Reflection: It can be defined as bouncing back of light, on the shiny smooth surface.
- It is done in a single medium no change of medium is seen.
- It follows law’s of reflection
1) Angle of incidence = Angle of reflection
2) The incident ray, the reflected ray, and normal to the surface of incidence always lies in the same plane.
Total Internal reflection: The total reflection of light from a higher refractive index medium to back in its medium at an angle more than a critical angle known as total internal reflection.
- It always happens when light travels from denser medium to rarer medium.
- At critical angle it makes 90° angle with normal separating two media.
- Sin = [where = rarer medium, = denser medium].
EXPLANATION:
A coin in a beaker filled with water appears raised because of Refraction.