The human eye is a conscious sense organ that allows light perception and vision. It acts like a Camera. It enables us to see the wonderful world and the colors around us. We will also study defects of the eye like myopia, hypermetropia, and presbyopia and its correction method. How will Refraction and Dispersion of light when it passes through the transparent prism? Also, we will understand the scientific reason for rainbow formation for primary and secondary rainbow types and also about atmospheric refraction. Further in the chapter, we will discover why the sun and surrounding sky appear red at sunrise and sunset.

In this virtual tour, we will learn about the human eye and the function of the different parts of the eye. The cornea, iris, pupil, ciliary body, lens, vitreous, retina, and optic nerve are various parts of the human eye. 

A person with myopia cannot see distant objects distinctly. It is corrected by using a concave lens of suitable power.

‘Refraction of the light’ means the bending of light when it goes from one medium to another. And ‘Dispersion of Light’ can be defined as the splitting of white light when it passes through a glass prism into its constituent spectrum of colors i.e. violet, indigo, blue, green, yellow, orange, and red.

The appearance of rainbows in the sky is due to the Dispersion of sunlight by the water droplets present in the atmosphere. The primary rainbow forms when the light is reflected once and the secondary rainbow forms when the light is reflected twice by raindrops. 

In this virtual tour, we will learn about atmospheric refraction, which is when a ray of light passes from one denser or rarer medium to the other rarer or denser medium in the atmosphere, it bends. It is known as atmospheric refraction.

We will understand how fluctuating density and deviation of ray, while it enters into the atmosphere of the twinkling of stars. The light rays from the stars are refracted in the atmosphere. The temperature and the density of layers keep changing. As a result, the path traveled by the light rays also keeps varying so that it gives an illusion of the star twinkling.

We will understand the principle behind sunlight and sunset. It is because of the refraction of light. When light travels from an optically rarer to an optically denser medium, it bends towards the normal. When the Sun is about to set, it is just below the horizon. The light from the Sun undergoes continuous refraction and follows a curved path in the atmosphere before reaching us. Its apparent position is, therefore, higher than its actual position. No wonder, we are able to see the Sun when it is still below the horizon! 

In this virtual tour, we will understand the concept of the Tyndall Effect. When a beam of light strikes on the tiny water droplets, suspended particles of dust, the path of the beam becomes visible due to light scattering. This is known as the Tyndall Effect.

As the white light from the Sun travels through the Earth’s atmosphere, it collides with particles of air. The different colors or wavelengths of light are scattered in different amounts. The molecules of air and other fine particles in the atmosphere have a size smaller than the wavelength of visible light. The color of the sky appears blue due to the scattering of light. The blue light has a shorter wavelength and so it is scattered much more than red or other light.

At the time of the sunset and sunrise, most of the blue and violet light get scattered before they reach our eyes. Due to this, the less scattered light like red or orange reaches our eyes which makes the sunrise or sunset appear reddish.

A person with hypermetropia cannot see nearby objects distinctly. It is corrected by using a convex lens of suitable power.

In presbyopia, the eye loses its power of accommodation at old age. It is a normal part of aging and can happen to anyone, even those with no provision problem. However, the condition can be easily corrected. This defect can be corrected by using a bifocal lens.