Specular reflection is very common and usually means a mirror like image. This can be seen in our daily life. This article first discusses what is reflection, types of reflection and then various examples of specular reflection.
What is Reflection?
As discussed in the sections above, light bounces back after falling on a polished or shiny surface. This phenomenon is called reflection.
When we look at ourselves in the mirror, it is because of reflection. Only polished surfaces can reflect light completely. Light will pass through the glass if it is transparent from both the sides. One side must be opaque to reflect the reflection of the glass. We will discuss how reflection happens in the sections below this article.
What is specular reflection?
Specular reflection is a type of reflection which means mirror-like reflection of light when it falls on a luminous body.
Specular obeys the law of reflection. The angle formed by my incident ray and the normal is the same as the angle and normal formed by the reflected ray. We will see more about the law of reflection and the mechanism of reflection in the sections below.
What is scattered/diffuse reflection?
Scattered Reflection Rays of reflection are scattered unevenly in all directions opposite to specular reflection.
In diffuse reflection, the reflected rays make unequal angles with the vertical. The reflected rays are scattered in several directions instead of one.
examples of specular reflection
Specular reflection can be seen everywhere in our daily life. Whenever we go to public places or sit inside our classrooms, one way or the other specular reflection can be observed.
Let us see more about specular reflection by looking at some examples. They are given below-
conventional plane mirror
A traditional rectangular plane mirror as we see in washrooms and wardrobes follows the principle of specular reflection. The incident rays come from the object standing in front of the mirror, these incident rays are reflected back at the same angle. Here, the angle of incidence is zero so the reflected ray also makes zero degrees with the normal mean, both the incident ray and the reflected ray intersect each other. The image of the object will be visible.
In concave mirrors, we can usually see an inverted image due to the curvature of the concave mirrors.
Glasses on the side walls of malls/shops
The mirrors on the side walls of the mall are thoroughly cleaned, thus making the mirrors a polished surface. So when we go near those glasses we can see our reflection on the glasses.
polished ceramic mug
A ceramic mug also acts like a mirror when it is properly polished. When we are holding the mug we see our reflection.
glow on sunglasses
When we clean the sunglasses, they become a polished surface. So the person standing in front of us can see his/her own reflection through our sunglasses.
Steel utensils also act as polished surfaces. If the object is placed near a mirror, we will be able to see its image. Metal body phone- Metallic finish acts like a polished surface, any light falling on such surface gets reflected back.
The body of the car is usually made of glass fiber which is given a polished finish. Due to the polished finish, we can see our reflections when we are standing near the car. A dirty car will not reflect our image because it is not polished.
A water body such as lakes and rivers is usually calm and reflects the objects around it. A perfect example of this is the reflection of the sky in a river and a lake. The lake appears blue due to the reflection of the sky.
polished plastic surface
When a plastic surface is polished, we can see our reflection on it. This is also due to specular reflection.
Radio waves are reflected in the ionosphere. This is an example of specular radiation of waves.
reflection of radar waves
When an enemy plane enters our airport, our radar detects it. This happens because the radar waves after hitting the aircraft are reflected back to the radar.
Sound can also be reflected using acoustic mirrors. This is an example of specular reflection of non-electromagnetic waves.
Atoms can be reflected by atomic mirrors. They also observe specular reflection.
A glossy paper used in crafts and decorative purposes, also reflecting light. This is also a specular reflection.
Most scissors are made of metal alloys and plastics. Both materials give a good reflection when polished.
The pupil of the eye also reflects light, when we look at the other person in the eye we can see our image in him.
How does specular reflection work?
In the above sections, we have discussed what is specular reflection. Now we will discuss how specular reflection works.
When an incident ray of light strikes a polished surface (also called a specular surface), it is reflected off the exact same angle at which the incident ray strikes the surface. A person standing in the path of the reflected ray would be able to observe the image of the source object from where the incident ray was coming.
How to calculate specular reflectance?
The specular reflectance can be calculated with the help of the Phong model which was developed by computer graphics researcher Bui Tong.
The specular reflectance is a dot product of two vectors. The formula is given below:
Specular reflectance = VR
where, V is the direction of view
R can be given by the formula given below-
r = 2. (nl) nl
L is the incident light direction
law of reflection
There are three defined laws of reflection in optics. They are given below-
- The angles subtended by the incident ray and the reflected ray with the normal are equal.
- The incident ray, reflected ray and normal all lie in the same plane.
- Both the incident ray and the reflected ray are on different sides of the normal.
Does specular reflection obey the law of reflection?
Specular reflection obeys the law of reflection. It satisfies all the conditions for which the laws of reflection are required. The incident ray makes the same angle with the normal as the reflected ray.
The reflected ray will be on one side of the normal and the incident ray will be on the other side of the normal. Then the most important thing is that all the three- normal, incident ray and reflected ray lie on the same plane. Therefore, we can say that specular reflection obeys all three laws of reflection.