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CBSE
CLASS 10 SCIENCE
CHAPTER11:HUMAN EYE AND THE COLOURFUL WORLD
NOTES
1. Structure of the Human Eye:
👉The human eye is roughly spherical in shape and is located in the eye socket of the skull.
👉The outermost layer of the eye is a tough, white, opaque sclera. The transparent bulge in the front is called the cornea.
👉The middle layer, the choroid, contains blood vessels that provide nourishment to the eye.
👉The innermost layer, the retina, consists of light-sensitive cells called photoreceptors.
2. Working of the Human Eye:
👉Light enters the eye through the cornea, which refracts the light and focuses it on the retina.
👉The iris, a colored muscular diaphragm, controls the amount of light entering the eye through its central opening called the pupil.
👉The lens, located behind the iris, further refracts the light and adjusts its focal length to focus the image on the retina.
👉The retina contains two types of photoreceptor cells: rods, which detect light intensity, and cones, which are responsible for color vision.
👉The photoreceptor cells convert light energy into electrical signals that are sent to the brain through the optic nerve.
👉The brain processes these signals to form the final visual perception.
3. Power of Accommodation:
👉The ability of the eye lens to adjust its focal length is known as the power of accommodation.
👉The ciliary muscles control the shape and thickness of the lens, enabling it to adjust its focal length.
👉The eye can focus on nearby objects by increasing the curvature of the lens (increase in power) and on distant objects by decreasing the curvature (decrease in power).
4. Defects of Vision:
👉The common defects of vision include myopia (nearsightedness) and hypermetropia (farsightedness), which result from the improper focusing of light.
👉Myopia occurs when the image is formed in front of the retina, and hypermetropia occurs when the image is formed behind the retina.
👉These defects can be corrected using appropriate lenses: concave lenses for myopia and convex lenses for hypermetropia.
5. Refraction of Light through a Prism:
👉A prism is a transparent triangular glass or plastic object that can refract light.
👉When light passes through a prism, it undergoes refraction and splits into its constituent colors, forming a spectrum.
👉The sequence of colors in a spectrum is known as the spectrum of white light.
6. Atmospheric Refraction:
👉The Earth's atmosphere acts as a medium for the refraction of light, causing various optical phenomena.
👉Sunrise and sunset appear earlier and longer due to atmospheric refraction, as light from the Sun bends while passing through the atmosphere.
👉Stars appear to twinkle due to atmospheric refraction caused by the turbulent layers of air in the atmosphere.
⭐These are the key points from Chapter 11 of the Class 10 NCERT Science textbook, "Human Eye and the Colourful World." It is recommended to refer to your textbook for detailed explanations, diagrams, and additional information.
