Light Class 8 Notes CBSE Science Chapter 13 (Free PDF Download)

1. Light is the natural agent that allows things to be visible to us. Light is being reflected from all surfaces and is a form of energy.

2. Objects which illuminate light on their own are known as luminous objects. Objects which do not give light on their own are said to be non-luminous objects. They reflect the light falling on them. When light is reflected from an object enters our eyes, and the object becomes visible to us.

3. Reflection of Light is the phenomenon of bouncing back of light after striking a shiny or polished surface, kept in the same medium.

4. Types of Reflection:

i. Regular Reflection: When a parallel beam of light rays incidents either on a smooth or on plane surface, the reflected rays will also be parallel. This is termed regular reflection. The reflection by a plane mirror is an instance of regular reflection.

ii. Diffused or Irregular Reflection: When the light ray incidents on a rough or uneven surface, it gets reflected in many directions because of the irregularities on that surface.

5. If the reflected light ray is reflected back again after the incident on another surface, then it is known to be multiple reflections. Multiple reflections is the principle on which periscopes work. Periscopes are mainly used in submarines, war tanks, and by soldiers in bunkers to see distant objects which are not visible directly. In a kaleidoscope, the same principle works as a result beautiful patterns are formed due to multiple reflections.

6. Laws of Reflection

i. The angle of incidence is equal to the angle of reflection.

ii. The incident ray, reflected ray and the normal drawn at the point of incidence to the reflecting surface lie in the same plane.

iii. Lateral inversion is the effect made by a plane mirror in reversing images from left to right. For instance, our left hand will appear as right in the mirror and vice versa.

7. The Characteristics of the Image Formed by a Plane Mirror:

i. Is the same size as that of the object

ii. Left-right inverted

iii. Erect and virtual

iv. Formed behind the mirror at the same distance as that of the object placed in front of the mirror.

8. Multiple images are formed when two mirrors are inclined to each other.

9. Sunlight, also known as white light, is made up of seven colors. The splitting of light into its constituent colors is termed as dispersion. Nearby and distant objects are clearly visible by a normal eye.

10. People that are blind can read and write by using the Braille system. They develop their other senses in order to improve their interaction with their environment.

11. Human Eye and its Parts

i. The front part of the eye is covered with a transparent spherical membrane known as the cornea. Light enters the eye by cornea. 

ii. Space present just behind the cornea contains a fluid known as aqueous humour.

iii. Just behind the cornea is a muscular diaphragm, which is dark coloured and is known as the iris which has a small circular opening in the middle called the pupil. The black colour of the pupil is due to no light being reflected from it. 

iv. The iris is responsible for controlling the amount of light entering the eye by adjusting the size of the pupil.

v. The lens of our eyes is a convex lens made of a transparent jelly-like proteinaceous material. The eye lens is hard in the middle and becomes soft towards the outer edges. 

vi. The ciliary muscles hold the eye lens in its position. The ciliary muscles are responsible for changing the curvature and focal length of the eye lens.

vii. The inner back surface of the eyeball is the retina. It is a semi-transparent membrane that is light sensitive and behaves as the screen of a camera. The light-sensitive receptors present in the retina are rods and cone cells. 

viii. The space between the retina and eye lens is filled with vitreous humour.

Light Class 8 Science Notes: Free PDF Download

The Law of Reflection

Light behaves in a very predictable manner. If a ray of light is observed while it is reflecting and approaching off a flat surface, the behaviour of this light, when reflected, follows a predictable law called the Law of Reflection. The ray of light approaches the mirror and this ray is called Incident Ray and the ray of light that leaves the mirror is called reflected ray. T

The law of reflection in class 8 science ch 13 notes will tell you that the point of incidence where this ray strikes and a line is drawn perpendicular to its surface is called a normal line. This line divides the angle between the reflected ray and the incident ray into equal angles. The angle of incidence is the angle which is formed between the incident ray and the normal ray. And the angle between normal and reflected ray is called the angle of reflection. 

Regular and Diffused Reflection

Regular and diffused reflection is an important part of light chapter class 8 notes. Regular reflection happens at the surface of a plane surface such as a plane mirror. The reflected rays after a regular reflection are parallel. And diffused reflection occurs at a surface of any rough surface like cardboard.

Ch 13 Science Class 8 Notes: Properties of Mirror Image

There are several properties of an image formed by a plane mirror. They are:

• They are of the same size as that of the object

• Left-right inverted

• Virtual and erect

• It occurs behind the mirror at the same distance as the distance of an object in front of the mirror.

Class 8 Chapter 13 Science Notes: Braille System

Braille system is an important part of class 8 science light chapter notes. It was discovered by Louis Braille specially designed for the blinds. It is a raised-dot writing which can be touched by the fingers and recognized. All the Braille characters are made of 6 dot positions which are arranged in a rectangle comprising a 2 column of 3 dots each. At any position, a dot can be raised. 

Braille codes consist of dot patterns of the alphabet, symbols and other punctuations. It is done by following a specific consistency and is referred to original assignments of Louise Braille. Also, different Braille codes are used to notate systems like mathematics, computer application and music and also chess. The basis of this code remains associated between 64 possible characters of Braille and the new notational elements.

Notes of Chapter Light Class 8: The Anatomy of the Eye

The human eye, as vividly described in Class 8 Science Chapter 13 Notes, has the following parts from outside to inside:

• The sclera which is also the white part of the eye protects our eyeball.

• The pupil is the opening of the eye through which the light enters.

• The iris surrounds the pupil and controls the amount of light that should enter the eye by changing the pupil’s size.

• The cornea present at the window in front of the eye helps to cover the pupil and the iris.

• There is a clear lens which is located behind the pupil and it acts as a camera by focusing light on the retina which is in the back of our eyes.

• The retina is a very important part of the eye. It is a sensitive lining present at the back of our eye. There are ten layers of a cell which help to detect light and as a result make it an electrical impulse.

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Conclusion

For an enhanced comprehension of this subject, NCERT - Class 8 Science Chapter 13 - Light, thoughtfully prepared by experienced educators at Vedantu, is your invaluable companion. These notes break down the complexities of Light into easily digestible sections, helping you grasp new concepts and navigate through questions effortlessly and quickly at the last minute as well. By immersing yourself in these notes, you not only prepare for your studies more efficiently but also develop a profound understanding of the subject matter.