Science Notes Class 8

Class 8

Science Notes

CHAPTER 10.5 COLOURS 

-The retina in the human eye has receptors which are sensitive to three colors - red, blue and green.This enables us to have color visions.

-Colored filters absorbs certain colors of light while transmitting others. E.g. a red filter transmits red light and absorbs the other colors of light 

-Red , Blue , and Green are the primary colors of light.They are formed by mixing two primary colors of light 

Book: International Lower Secondary Science 3

By: Tajwar Rasheed

Science Notes Class 8

Class 8

Science Notes 

CHAPTER 10.4 REFRACTION OF LIGHT

-The bending of light when it travels from one transparent medium to another to another is called refraction of light

-Refraction of light occurs because light travels at different speeds in different media

-Light bends towards the normal when it's speed decreases as it passes from one medium to another. It bends away from the normal when its speed increases as it passes from one medium to another

-Apparent depth and dispersion of white light are effects of refraction

Book: International Lower Secondary Science 3

By: Tajwar Rasheed

Science Notes Class 8

Class 8
Science Notes

CHAPTER 10.3 REFLECTION OF LIGHT

-Light can reflect or bounce off when it strikes a surface
-The angle of incidence is the angle b/w the incident ray and the normal while the angle of reflection
is the angle b/w the reflected ray and normal
-The angle of incidence is equal to the angle of reflection
-Smooth surfaces of glass and polished metals produces regular reflection. A parallel beam of light striking a smooth surface is reflected as a parallel beam
-Rough surfaces of paper or wood produces diffused or scattered reflection
-Images formed by a plane mirror are virtual,upright,laterally inverted,same in size and as far behind the mirror as the objects are in the front
-Plane mirror are used as rear-view mirror in cars and in optical instruments such as microscopes,reflecting telescopes and periscopes
-Convex mirrors produce s upright and give a wide scope of view.They are used as security mirrors,car wing mirrors and blind corner mirrors.
-Concave mirrors produces magnified objects are near to the mirror.They are used as dentist's mirror and cosmetic mirrors

Book: International Lower Secondary Science 3

By: Tajwar Rasheed

Science Notes Class 8

Class 8
Science Notes

CHAPTER 10.2 SHADOWS
-A shadow is a region of darkness formed when the path of light is blocked.
-Shadows are formed because light travels in a straight line.
-Light can not bend around the object to reach the back,thus a region of darkness where light cannot reach is formed behind the object
-For an extended source of light,the shadow formed consist of a dark region called an Umbra and a partial shadow called a Penumbra

Science Notes Class 8

Class 8
Science Notes

CHAPTER 10 LIGHT ;
-Light is a form of energy which can be detected by our eyes. It can travel through vacuum and different media
-The speed of light in vacuum is 300'000'000 m/s
-Light travels at different speeds in different media
-Light travels in a straight line in the same media
-The path along which light travels is called a Ray
-A beam of light is made up of a bundle of rays. It can be parallel,divergent or convergent
-Some objects are able to give out their on light. These objects are said to be luminous objects
-Objects which do not give out their own light are said to be non-luminous objects
-When light falls on an object it can be reflected,transmitted or absorbed 
-Transparent materials allows almost all the light to pass through
-Translucent materials allows some light to pass through.
-Opaque materials do not allows light to pass through.

Book : International Lower Secondary Science 3
By : Tajwar Rasheed