Laws of reflection
It's only because of light we are able to see this world around us
So what happens is, when light falls on the surface of an object, it returns back or reflects the light
This reflected light falls in our eyes, and this is how we see the objects
Here, bouncing off light when it hits an object is called Reflection
But while reflecting from mirrors, Light follows few laws. Which we will discuss them in Laws of Reflection
The first law of reflection states that the angle of incidence = Angle of reflection
The angle of Incidence is the angle that an incident ray makes with a perpendicular to the surface at the point where light falls
The angle of Refraction is the angle that a reflected ray makes with a perpendicular to the surface at the point where light bounces off
The second law of reflection states that the incident ray, the reflected ray and the normal to the surface lie in the same plane
The plane contains the incident rays, reflected rays and the normal
Let us try to understand more about the laws of reflection by solving a problem
Let's consider an incident ray and the reflected ray falling on a mirror are perpendicular to each other
Then, we have to find the angle of incidence
Let's construct the general diagram showing the incident ray, reflected ray and the normal
We have already considered the second law of reflection that all the rays are in the same plane while constructing this figure,
But, we have been told in the problem that the incident ray and the reflected ray are perpendicular to each other
Hence, we can say that
$i+r$
= 90°
But, from the first law of reflection, we have
$i=r$
Hence,
$i+i$
= 90°
$2i$
= 90°
$i$
= 45°
Hence, we get the angle of incidence = 45°
This is the final diagram showing the angle of incidence and the angle of reflection
Revision
We have discussed the Laws of Reflection
$1_{st}lawofreflection$
says that the angle of incidence and reflection are equal
$2_{nd}lawofreflection$
says that the incident reflected and normal rays lie in the same plane
Given in the problem, the incident ray and the reflected ray are perpendicular to each other. Hence,
$i+r$
=90°. We have to find
$i$
But we know
$i=r$
$i+i$
= 90°
$⟹$
$2i$
= 90°
$⟹$
$i$
= 45°.
Hence the Angle of Incidence = 45°
The End