Introduction
The human eye uses light and enables us to see objects around us.
The Eye
Our eye is the most important natural optical instrument. The eye is nearly spherical in shape with a slight bulge in the front part.
Working of an Eye
The light coming from an object enters the eye through cornea and pupil. The eye lens converges these light rays to form a real, inverted and diminished image on the retina.
Power of Accommodation
The process by which the ciliary muscles change the focal length of an eye lens to focus distant or near objects clearly on the retina is called the accommodation of the eye.
Defects of Vision
A normal eye can see all objects over a wide range of distances i.e., from 25 cm to infinity
Astigmatism
Astigmatism is the most common vision problem resulting in distorted images, as light rays are prevented from meeting at a common focus.
Hypermetropia
You must have seen middle aged people holding a book away from their eyes to read properly.
Myopia
A myopic person cannot see distant objects clearly because the far point of his eye is less than infinity.
Presbyopia
Presbyopia is caused when the centre of the eye lens hardens making it unable to accommodate near vision. This condition generally affects almost everyone over the age of 50 - even those with myopia
Newton's Experiment - Dispersion of Light
Sir Isaac Newton, while studying the images of heavenly bodies formed by a lens, found that the images were coloured at the edges.
Tracing the Path of Light Through a Prism
Angle of deviation is the angle through which an incident ray deviates.Repeat this for different values of angle of incidence.
Dispersion of White Light By a Glass Prism
Even though all colours of the visible spectrum travel with the same speed in vacuum, the speed of the colours of the visible spectrum varies when they pass through a transparent medium like glass and water.
Recomposition of White Light
Recombination of the seven colours of the dispersed white light to get white light is known as recomposition of white light.
Atmospheric Refraction
Atmospheric refraction is the shift in apparent direction of a celestial object caused by the refraction of light rays as they pass through Earth’s atmosphere.
Scattering of Light
Scattering is a general physical process whereby some forms of radiation, such as light or moving particles, for example, are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which it passes.
Summary
The process by which the ciliary muscles change the focal length of an eye lens to focus distant or near objects clearly on the retina is called the accommodation of the eye.
Question and Answers
Question and Answers 1
Multiple Choice Questions
