You can see the rainbow in the sky when the sun shines, but you cannot see anything in the dark. The entire credit goes to your eyes that enable you to see the colourful rainbow. Did you wonder why you cannot see things in the dark even with your eyes open? Have you ever thought of science behind the law of light? It is because your eyes can see objects when an object emits light or reflects light.
Furthermore, you often turn to a mirror or any other shiny object to get a glimpse of your appearance. Whenever light falls on a mirror, it changes the direction of light. However, what we can see depends upon the direction of the light it reflects.
The bouncing back of light rays from the surface of an object is called reflection. To get a clear picture of the laws of reflection you need to understand different terms of lights, rays and angles.
The light which falls on an object is called incident ray.
The ray of light which gets reflected from the surface is called reflected ray.
Angle of Incidence in Law of Light
The angle of incidence is the angle established between the incident ray and normal at the point of incidence.
Angle of Reflection in Law of Light
The angle derived between the reflected ray and normal is called the angle of reflection.
Normal to the reflecting surface at that point is when a line makes an angle of 90° to the line of the mirror at the point where the incident ray strikes the mirror.
When a ray of light gets reflected from the smooth, shiny surface, it obeys specific laws. These are laws of reflection.
The first law of reflection states that the reflection angle is always equivalent to the angle of incidence. If the incident ray falls on the plane mirror along the normal, i.e. 90°, the reflected ray will travel along the same path
The incident ray, reflected ray, angle of incidence and reflection, and point of incidence lie on the same plane.
Under the law of light, there are two types of reflection depending upon its surface – regular and irregular or diffused reflection.
Laws of Light on a Plane Surface
Regular reflection is a condition when light reflects in the same direction from a smooth or plane surface. Let us understand this with an example. Suppose an object is placed before the mirror, a smooth surface, the reflecting light of parallel ray will be parallel. The image on the left of the object appears on the right, and the image on the right appears on the left. Such reflection is known as lateral inversion.
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Laws of Light on a Rough Surface
Irregular or diffused reflection is a condition when light reflects in an irregular pattern from a rough surface. Let us understand this with an example. Suppose light falls upon a wall. The reflection of parallel rays of light will not be parallel. The reflecting light spreads in different directions. Here also the law of reflection of light is working.
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You can see beautiful patterns in a kaleidoscope because of multiple reflections from the mirror placed inside it.
The sunlight is a white light which also consists of seven colours of the rainbow which we can see after the rainfall.
When you stand before an inclined two mirrors, you can see multiple images of yourself.
The moon receives the light from the sun, which makes it illuminate. Thus, we can see the moon at night.
Periscope is an excellent example of reflection from the two mirrors that enables you to see far-away objects. They are used by soldiers in bunkers at the border. Furthermore, submarines and tanks also have an inbuilt periscope.
Q1. How Many Types of Reflection are There?
A1. There are two types of reflection depending upon the nature of the reflecting surface. The reflection from a smooth surface differs from the reflection of a rough surface.
When a ray of light falls on a smooth and shiny reflecting surface, it gets reflected in a particular direction. Reflection of light from a smooth surface, such as mirror, a stainless steel plate, etc. is called regular reflection.
When a ray of light falls on an uneven surface, they get reflected in diverse directions. As a result, the reflected ray falls over a larger area, and the image formed is not sharp and clear. Such reflection is irregular or diffused reflection. Reflection of light from a wall, a paper, and many other everyday objects is irregular or diffused reflection.
Q2. Explain how Multiple Images are Formed with an Example. Justify your Answer with the Factors.
A2. If you want to see multiple images of yourself, then you will need to place more mirrors at different angles. Multiple reflections are the phenomenon in which you can see multiple images because the images formed by one mirror acts as an object for the second mirror. The number of visible images is determined depending upon the angle at which the second mirror is placed. You can calculate the number of images formed using the following formula.
Number of images = (360°/ angle of placement) – 1
Suppose, you place a candle between two mirrors, which is at a distance of 40 cm from each other, the number of images of candles between two parallel mirrors is infinite. The angle is considered to be 0° which results in an infinite number of images.