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This content is part of NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World

Question 1. What is meant by power of accommodation of the eye? Answer: The power Of accommodation of the eye is the ability of the eye to observe the distinct objects clearly which are situated at a large distance from the eye. The ciliary muscles are responsible to change the focal length Of the eye lens. The value of the power of accommodation Of the normal human eye is (d = 25 cm) = 100/f = 100/d = 100/25 = 4 dioptres. The value of power of accommodation Of human eye is about 4D

LIGHT :

This content is part of NCERT Solutions for Class 10 Science Chapter 10 Light Reflection and Refraction

Light is a form of electromagnetic energy that causes the sensation of vision.

           Optics :

             It is the branch of physics which deals with the study of light. It is mainly divided into three parts :

             (i) Geometrical optical or ray options: It deals with the reflection or refraction.

             (ii) Wave or physical optics: It is concerned with nature of light and deals with interference diffraction and

polarisation.      

(iii) Quantum optics : It deals with the interaction of light with the atomic entities of matter such as photo

electric effect, Atomic excitation etc.

 1.1 (a) Nature of Light :

             Theories about nature of light :

             (i)         Particle nature of light (Newton’s corpuscular theory(: According to Newton light travels in

space with a great speed as a stream of very small particles called corpuscles.

This content is part of NCERT Solutions for Class 10 Science Chapter 6 Life Processes

INTRODUCTION :

All living organisms have arisen through the evolutionary process and show diversity, yet some similarities exist among them. e.g. Amphibians, reptiles and mammals have limbs for locomotion in water, fishes have fins for swimming in water and birds have wings for flying.

               •      A close examination reveals that the limb, fins and wings are formed on the same basic structural plan.

               •      All such examples can be explained if we consider that the diverse groups of organisms share a common ancestor from who they have diverged and formed two different species. Such process of change in biological system is called as evolution.

               •      The Doctrine of the Organic Evolution state that the organisms existing at present are the descendants of much simpler ancestors.

 16.2     EVOLUTION :

This content is part of NCERT Solutions for Class 10 Science Chapter 15 Our Environment

ECOSYSTEM :

               •      The term Ecosystem was coined by Tansley. According to him Ecosystem is a symbol of structure and function of nature.

               •      The term Ecology was coined by Reiter.

               •      The term Ecology was first of all described y  E.Haeckel.

               •      Father of India Ecology - Prof. Ramdas Mishra.

                        *8    The boundaries of ecosystem are indistinct and have an overlapping character with each other.

               •      “The total group of living things and environment of factors present in a particular place is called as ecosystem/”

               •      It means any structural and functional unit of the environment that can be identified and studied is called as ecosystem.

               •      Ecosystem may be natural or artificial, permanent or temporary. Large ecosystem is called as biome such as desert, forest etc.

               •      Homeostasis : Self maintainable characteristic is found in ecosystem. It means an ecosystem maintains the balance between the different trophic levels. Each trophic level controls the other trophic level in an ecosystem.

This content is part of NCERT Solutions for Class 10 Science Chapter 5 Periodic Classification of Elements

DEFINITION :

A periodic table may be defined as the table giving the arrangement of all the known elements according to their properties so that elements with similar properties fall with the same vertical column and elements with dissimilar properties are separated.

17.2     EARLY ATTAMPTS TO CLASSIFY ELEMENTS :

17.2     (a) Metals and Non - Metals :

ACIDS :

This content is part of NCERT Solutions for Class 10 Science Chapter 2 Acids Bases and Salts

Substances with sour taste are regarded as avoids. Lemon juice, vinegar, grape fruit juice and spoilt milk etc. taste sour since they are acidic. Many substances can be identified as acids based on their taste but some fo the acids like sulphuric acid have very strong action on the skin which means that they are corrosive in nature. In such case it would be according to modern definition-

           An acid may be defined as a substance which release one or more H+ ions in aqueous solution.

           Acids are mostly obtained from natural sources. One the basis of their source avids are of two types -

             (a) Mineral acids                                           (b) Organic acids

 4.1 (a) Mineral Acids :

             Acids which are obtained from rocks and minerals are called mineral acids.

 4.1 (b) Organic Acids :