The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:
The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:
Introduction
Have you ever thought of a life where there is no light? A world that is dark and does let us appreciate the beauty of nature? If not for the light that the Sun blesses us with, the sense of sight too has no meaning to it.
It, therefore, becomes important that you understand the concept of light and its importance in nature.
When light reflects from a surface, that surface becomes visible to the human eye.
Let us learn how a ray of light makes things visible by understanding the concepts of Incident ray, Reflected ray, and a Normal.
Case: Imagine a mirror placed on a plane surface opposite to which, a black screen is placed with a small gap in it. Now position a torch (as our source of light) in such a manner that the ray of light coming out of the torch will pass through the gap in the black screen and fall on a point on the mirror.
Incident ray: The ray of light that falls on the mirror is called the incident ray.
Reflected ray: The same ray of light when it reflects back from the mirror surface is called the reflected ray.
Normal: If we draw a straight line at 90° perpendicular to the mirror surface at the point where the light falls on the mirror, this straight line is called Normal.
To understand the laws of reflection, you must first understand the following terms:
Angle of incidence: The angle between the Normal and the incident ray is the angle of incidence.
Angle of reflection: The angle between the Normal and the reflected ray is the angle of reflection.
1) First law of reflection: The angle of incidence is always equal to the angle of reflection. Even If you change the angle of incidence, the angle formed by the reflected ray will still be equal to that formed by the incident ray.
2) Second law of reflection: The incident ray, the Normal (at the incidence point), and the reflected ray all lie in the same plane always. If you experiment by adding a break in the plane where the incident ray and Normal are present, it will result in the formation of a new plane. Due to this new plane, the reflected ray is not visible, thus proving the second law of reflection.
Due to this new plane, the reflected ray is not visible, thus proving the second law of reflection.
Reflection depends on the surface of reflection. If the surface of reflection is smooth like that of a mirror, the reflection of light is called regular reflection.
If the reflection surface is irregular (such as the surface of the moon), the reflection of light is called irregular or diffused reflection.
Imagine having more than one mirror at any angle to each other or parallel. This will lead to multiple images from the same light, which tells us that reflected light can be reflected again.
This principle is used in Kaleidoscope.
The sunlight is made of seven distinct colours. You have already studied them in class VII with the concept of VIBGYOR, the colours of sunlight.
When light passes through water and mirror or through a prism, it splits into its individual colours. This phenomenon is seen in a rainbow.
The reflected light can be seen only when it enters our eyes. Being one of the most important sensory organs, you must understand the structure of eyes.
Within the outer tough white layer, there is a transparent inner layer called cornea. It is behind the cornea that we can find the muscular structure called iris that hosts the pupil. The colour of the eyes is decided by the iris. Behind the iris is the lens which monitors the amount of light that enters the eyes and focuses the light on the inner retina. It is the retina that passes signals to the brain via its numerous neural connections, thus forming images in the eyes.
Nature has protected our eyes by giving it eyelids. But we must take special care of our eyes by these simple practices:
Visually impaired persons can read and write
People with limited to no vision can also read and write with external help. Their other senses get sharper too. Visually impaired people can read and write with the following assistance:
1) Lenses such as contact, bifocal, etc
2) Visual, tactual, auditory, and electronic aids.
Braille system
It is a tactual aid developed by Louis Braille for visually impaired people. It consists of a pattern of dots that represent letters and words. These patterns are embossed on sheets so that visually challenged people can recognize words by touching them.
1) What is light?
Light is an underrated gift of nature without which, everything will be black and colours will not be recognized.
2) What is light called?
It is also referred to as electromagnetic waves.
3) What are the properties of light?
The important properties of light are: it travels in a straight line, the speed of light is faster than sound, and the phenomenon of reflection of light.
4) What are the 7 types of light?
The white light is made up of the following 7 colours: Red, Orange, Yellow, Green, Blue, Indigo, and Violet.
5) Is white light just white?
No, white light when reflected through a prism splits into its 7 colours otherwise not visible to naked eye.
The topic of Light can be understood better by referring to MSVgo, a learning app. It is a video learning app on Maths and Science for students from class 6th to 12th. Check out the app and understand the concept of Light through its interactive animations and explanations.
