When light strikes a surface, a portion of it is sent back into the same medium, termed as reflected light. If the surface is opaque, the remaining light is absorbed. However, if the surface is transparent, some of the light passes through while the rest is absorbed.
Reflection is the phenomenon where light bounces back into the same medium upon hitting a surface. It’s crucial for our perception of the world as it allows us to see objects. While luminous bodies emit their own light and are directly visible, non-luminous objects become visible by reflecting incident light into our eyes.
Reflections occur in two main types:
1. Regular reflection (specular reflection)
2. Irregular reflection
Regular reflection (specular reflection):
Regular reflection happens when a parallel beam of light encounters a smooth, polished surface, bouncing off in a parallel manner but in a different direction. Mirrors, still water, and highly polished metals demonstrate regular reflection, contributing to the formation of clear images. However, it can lead to strong glare.
Irregular reflection:
In contrast, irregular reflection, also known as diffused reflection, occurs when a parallel beam of light hits a rough
surface, causing it to reflect in various directions. This type of reflection is common on surfaces like the ground, walls, and trees, as well as suspended particles in the air. Irregular reflection disperses light energy over a wide area, reducing its intensity and aiding in general illumination.
The Laws of Reflection govern both types:
The incident ray, the reflected ray, and the normal (a line perpendicular to the surface at the point of incidence) all lie in the same plane.
The angle of incidence equals the angle of reflection.
Note:
- The angle of deviation for a ray hitting a plane mirror is given by:
d = 180° − 2i or 180°−2r,
where i represents the angle of incidence and r the angle of reflection.
- The glancing angle (g) can be calculated as,
g = 90° − i or 90° − r or d/2,
where d stands for the angle of deviation.
