Extra Question Chapter 1:Chemical Reaction And Equations
Extra Question II Chapter 1:Chemical Reaction And Equations
Extra Question Chapter 2:Acid Ans Base
Important Question Chapter 3:Metal and Non Metal
Chapter 4:Carbon And Its Compoundl
Chapter 5:Periodic Classification of elememt
Chapter 7:Control and coordination
Chapter 8:How Do Organisms Reproduce?
Chapter 9:Hearedity And Evolution
Chapter 10:Light Reflection and Refraction
Chapter 11:The Human Eye and Colorful World
The human eye is a complex organ structured to receive light and transmit the interpreted information to the brain. It consists of various parts like the cornea, iris, pupil, lens, retina, and optic nerve. The cornea is the clear front surface that allows light to enter. The iris is the colored part that controls the light's amount that enters the eye by adjusting the pupil's size. The lens focuses the incoming light onto the retina, which is filled with light-sensitive cells that trigger nerve impulses. These impulses are then sent to the brain via the optic nerve, which interprets them as images.
Myopia, also known as nearsightedness, is a condition where the eye can see close objects clearly, but distant objects appear blurry. This occurs when the eye is longer than normal or the cornea is excessively curved, causing light to focus in front of the retina instead of directly on its surface. Myopia can be corrected with glasses, contact lenses, or refractive surgery. These corrective methods aim to reduce the eye's focusing power by moving the focus point back onto the retina.
Hypermetropia, or farsightedness, is a condition where distant objects can be seen clearly, but close ones appear blurry. This happens when the eye is shorter than normal, causing light to focus behind the retina. Hypermetropia can be corrected with glasses or contact lenses that have a 'converging' or convex lens. This increases the eye's focusing power and moves the focus point onto the retina. Refractive surgery is another option for correction.
Presbyopia is an age-related condition where the ability to focus up close becomes more difficult. As the eye ages, the lens can lose its ability to change shape enough to allow the eye to focus close objects clearly. Presbyopia is corrected with reading glasses or bifocal lenses.
The blind spot is an area on the retina where the optic nerve leaves the eye. This area is called the blind spot because it lacks photoreceptors, so light focused on this spot cannot be seen.
Color blindness is a genetic condition where a person can't distinguish between certain colors. This condition is caused by an absence or malfunction of certain color-sensitive cells in the retina. The most common form is red-green color blindness, where individuals have difficulty telling the difference between red and green.
Color perception starts with light entering the eye and being absorbed by special cells in the retina called cones. Humans usually have three types of cones that are sensitive to short wavelengths (blue), middle wavelengths (green), and long wavelengths (red). The brain combines the information from these different types of cones to perceive all the possible colors.
A rainbow is formed when white light, like sunlight, is broken up into its component colors by water droplets in the atmosphere. This process, known as dispersion, causes the light to spread out into a range of colors from red to violet. Each droplet of water acts as a tiny prism, refracting or bending the light, reflecting it inside on the back of the droplet, and refracting it again as it exits the droplet. This creates the spectrum of colors we see in a rainbow..
The power of accommodation refers to the eye's ability to adjust its focus from distant to near objects. The lens changes its shape to focus light on the retina. For distant objects, the lens becomes thinner, and for close objects, it becomes thicker. This adjustment in focus is known as accommodation.
Stars twinkle because of the way light is affected as it passes through the Earth's atmosphere. This phenomenon, known as astronomical scintillation, is caused by variations in air density in the atmosphere that refract or bend the path of light, causing it to shift direction rapidly. To observers on the ground, this shifting appears as a twinkling effect.
A "blue moon" doesn't refer to the moon's color. Instead, it refers to the occurrence of two full moons within one calendar month
Dispersion of light is the process by which white light is separated into its component colors when passing through a medium such as a glass prism. This occurs because different colors (or wavelengths) of light are refracted, or bent, by different amounts as they pass through the medium
The iris is the colored part of the eye. It controls the size of the pupil and thus the amount of light that enters the eye. In dim light, the iris widens the pupil to allow more light in. In bright light, it narrows the pupil to limit the amount of light entering the eye
The lens of the eye is a clear, flexible structure that sits behind the iris. Its primary function is to focus light onto the retina. It does this by changing shape – it flattens to focus on distant objects and thickens to focus on near objects.
Rods and cones are types of photoreceptor cells in the retina of the eye. Cones are responsible for color vision and function best in relatively bright light conditions. Rods, on the other hand, do not distinguish colors, but are responsible for vision in low light conditions.
The Tyndall effect, also known as Tyndall scattering, is the scattering of light by particles in a colloid or in a very fine suspension. This effect causes beams of light to become visible, like a beam of sunlight in a room filled with smoke. The color of the scattered light depends on the size of the particles and the wavelength of the light. .