Human Eye and Colourful World, CBSE CLASS X, PHYSICS NOTES PART I

 CBSE CLASS 11, Human Eye and Colourful World, PHYSICS NOTES-(PART I)

Human Eye and Colourful World


According to the CBSE Syllabus 2025-26

CBSE Class 10 Science Chapter 10th Human Eye and Colourful World Notes

Study Material and Notes of Ch 11 Human Eye and Colourful World Class 10th Science

TOPICS IN THE CHAPTER

(1) Introduction
(2) Parts of Human Eye
a. Cornea
b. Lens
c. Iris
e. Pupil
f. Retina
(3) Near point or Least distance of distinct vision
a. Accomodation
(4) Myopia (Near sightedness)
a. Causes of Myopia
b. Correction of Myopia
(5) Hypermetropia
a. Causes of Hypermetropia
b. Correction of Hypermetropia
(6) Presbyopia (Old age Hypermetropia)
a. Causes of Presbyopia
b. Correction of Presbyopia
(7) Advantage of the eyes in front of the face
(8) Refraction through a glass prism
a. Prism
b. Angle of Prism
c. Angle of deviation (d)
d. Spectrum
e. Acronym
(9) Total internal reflection
a. Conditions necessary for Internal Reflection
b. Critical Angle
c. Rainbow
d. Atmospheric Rainbow
e. Advanced Sunrise
f. Twinkling of stars
(10) Scattering Effect
a. Tyndall effect
(11) Dependance of colour of scattered light
a. Anger signs are made in red colour
b. Colour of sky appears blue on a clear day
c. Appearance of sky to an astronaut in the space
d. Clouds appear white
e. Colour of sun appear red during sunrise and sunset

 

CBSE Class 10 Science Chapter 11 The Human Eye and the Colourful World Notes

 

Using the knowledge of light and some of its properties which students study in the previous chapters, students study how these concepts apply to the human eye in the class 10 Science chapter, The Human Eye and the Colourful World. Students also study some of the optical phenomena. The nature and the formation of the rainbow, the splitting of white light and the blue colour of the sky are also examined in the chapter.

 

INTRODUCTION

 

→ Human eye: The sense organ that helps us to see.
→ Located in eye sockets in skull.
→ Diameter of eye ball – 2.3 cm.

 

STRUCTURE OF A HUMAN EYE

 

Of all the sense organs, the human eye is the most significant one as it enables us to see the beautiful, colourful world around us. The eye is spherical in shape and has a diameter of 2.3 cm on average. The internal structure of the eye includes- the cornea, iris, pupil, lens, ciliary muscles, retina, nerve cells, optic nerve, yellow spot, aqueous and vitreous humor, and suspensory ligament.

The lens system of the human eye forms an image on the light-sensitive screen called the retina. The cornea is the thin membrane of the eye through which light enters. Most of the light refraction occurs at the outer surface of the cornea. A dark muscular diaphragm that controls the size of the pupil, known as the Iris is present behind the cornea. The pupil is a structure in the eye that controls and regulates the amount of light entering the eye. The light-sensitive cells get triggered upon illumination and induce electrical signals. These signals are sent to the brain through the optic nerves. The brain analyses these signals and, finally, processes the information so that we sense objects as they are.

 

PARTS OF HUMAN EYE

a. CORNEA:

It is the outermost, transparent part. It provides most of the refraction of light.

b. LENS: 

It is composed of a fibrous, jelly like material. Provides the focused real and inverted image of the object on the retina. This is convex lens that converges light at retina.

c. IRIS: 

It is a dark muscular diaphragm that controls the size of the pupil.

d. PUPIL: 

It is the window of the eye. It is the central aperture in iris. It regulates and controls the amount of light entering the eye.

e. RETINA: 

It is a delicate membrane having enormous number of light sensitive cells.

f. FAR POINT: 

The maximum distance at which object can be seen clearly is far point of the eye. For a normal adult eye, its value is infinity.

 

NEAR POINT OR LEAST DISTANCE OF DISTINCT VISION

 

The minimum distance at which objects can be seen most distinctively without strain. For a normal adult eye, its value is 25 cm. Range of human vision – 25 cm to infinity.

 

ACCOMODATION:

 

The ability of the eye lens to adjust its focal length is called accommodation. Focal length can be changed with the help of ciliary muscles. Focal length increases when Ciliary muscles get relaxed and lens get thin. Focal length decreases when Ciliary muscles get contract and lens get thick.


DEFECTS OF A HUMAN EYE

There are few common eye disorders seen in all individuals, and they are caused by several factors. These conditions can be improved by the corrections. The defects include:

 

MYOPIA (Near sightedness)

 

This is also called short-sightedness. A person with this eye defect can only see nearby objects clearly compared to distant objects. Image is formed in front of retina.This condition can be corrected using a concave lens.

 

CAUSES OF MYOPIA

 

a. Excessive curvature of eye lens.

b. Elongation of eye ball

 CORRECTION OF MYOPIA

 It is done by using a concave lens of appropriate power.                                                                 

(i) In a myopic eye, the image of a distant object is formed in front of the retina. (and not on the retina)                                                                                                                                                  

(ii) The far point (F) of a myopic eye is less than infinity.

(iii) Correction of myopia. The concave lens placed in front of the eye forms a virtual image of a distant object at the far point (F) of the myopic eye.


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