The human eyeis an organ that detects light and allows us to see. It works like a camera by focusing light onto the retina, which sends signals to the brain to form an image.
Parts of the Human Eye:
- Cornea – Transparent outer layer that refracts light.
- Pupil – The dark circular opening that controls the amount of light entering the eye.
- Iris – The colored part of the eye that controls the size of the pupil.
- Lens – Focuses light onto the retina.
- Retina – The light-sensitive layer at the back of the eye where images are formed.
- Optic Nerve – Transmits the visual information from the retina to the brain.
Working of the Eye:
- Light enters through the cornea and pupil.
- It is focused by the lens onto the retina.
- The retina converts the light into nerve signals, which are sent to the brain through the optic nerve.
The Colourful World:
The world appears colourful because light from the sun is made of different colours (the spectrum of light).
- Dispersion of Light:When white light passes through a prism, it splits into its seven colours (violet, indigo, blue, green, yellow, orange, and red) — this is called dispersion.
- The Formation of Rainbow: A rainbow is formed when sunlight is refracted and dispersed by water droplets in the sky, creating a spectrum of colours.
- Why the Sky Appears Blue: The blue light from the sun is scattered more than other colours due to its shorter wavelength, making the sky look blue.
Practice Questions PDF
Download a printable worksheet on The Human Eye and the Colourful World with answers.
Questions on The Human Eye and the Colourful World
Showing 31–60 of 8231.A light ray enters a water droplet from the air. It strikes the inner surface of the water droplet and undergoes total internal reflection. Which condition must be met for this total internal reflection to occur? 32.Compare the function of the retina in the human eye with a part of a photographic camera. 33.What is presbyopia? How is it corrected? 34.An astronaut in space finds the sky to be dark instead of blue. Why? 35.A person uses a convex lens of focal length 25 cm to read a book. What is the power of this lens? 36.Explain why we see the Sun two minutes before the actual sunrise and two minutes after the actual sunset. 37.Differentiate between rod cells and cone cells in the retina. 38.What is the role of the ciliary muscles in the human eye? 39.Which part of the human eye controls the amount of light entering the eye? 40.Describe the formation of a rainbow. 41.A person can see objects clearly only when they are between 50 cm and 400 cm from his eyes. What type of corrective lenses would he need, and what would be their power, to restore normal vision (i.e., be able to see distant objects and objects at 25 cm)? 42.Why is the Tyndall effect observed when light passes through a colloidal solution but not through a true solution? 43.Draw a labelled diagram to show the dispersion of white light by a glass prism. Write the sequence of colours observed on the screen. 44.Stars twinkle but planets do not. Explain this phenomenon. 45.Why does the Sun appear reddish at sunrise and sunset? 46.The sky appears blue during the day. Explain why. 47.A student sitting on the last bench in the class complains that he is unable to read the writing on the blackboard. What is the likely defect of vision he is suffering from? How is this defect corrected? 48.Why can a person with myopia not see distant objects clearly? How is this defect corrected? 49.A person needs a lens of power -5.5 D for correcting his distant vision. For correcting his near vision, he needs a lens of power +1.5 D. Calculate the focal length of the lens required for correcting (i) distant vision and (ii) near vision. 50.What is hypermetropia? 51.Can visible light be scattered by atoms/molecules in the earth’s atmosphere? 52.Why do different colours deviate through different angles on passing through a prism? 53.What is the function of the optic nerve in the human eye? 54.Why are we not able to see things clearly when we come out of a dark room? 55.Why do we observe random wavering or flicking of the objects near a fire or on a very hot day? 56.State the role of the eye lenses in the human eye? 57.Why is a convex lens called a converging lens? 58.What is the role of the ciliary muscles? 59.State the difference in colours of the sun observed during sunrise/sunset and noon. Give explanation for each. 60.Why does the sun appear reddish early in the morning? Will this phenomenon be observed by an astronaut on the Moon? Give reason to justify your answer.