INTRODUCTION: HUMAN EYE -The human eye is a sensory organ that allows us to see objects around us. -It operates like a camera, forming an image of an item on the retina. -The retina is the eye’s light-sensitive screen, where images are created. -The image created is real, inverted, and smaller in size; but our brain interprets it as upright. -The eye lens is convex in shape, and the focus length may be changed to observe both nearby and distant things. -The average adult human eye has a focus length of around 2 cm and a diameter of approximately 2.3 cm. -The human eye can see objects clearly from around 25 cm (near point) to infinity (far point). Check out related Question-Answers: Visit QnA.Gyanora.in or PARTS OF HUMAN EYE Cornea Iris Pupil Eye Lens Retina Ciliary Muscles Optic Nerve Aqueous Humour Vitreous Humour Check out related Question-Answers: Visit QnA.Gyanora.in or HUMAN EYE WORK AS A CAMERA The human eye works like a camera in many ways, like: 1.The Lens of the Eye: Just as a camera lens focusses light, your cornea and eye lens bend light rays to create a sharp image inside. 2. The Aperture: The aperture in a camera determines how much light enters. The pupil in your eye performs this function. The pupil contracts in bright sunshine and expands in low light. 3. The shutter: Cameras employ shutters to open and close. Your eyelids act as natural shutters, shielding your eyes and providing slumber. 4. The Film or Screen: Camera capture images on a film or sensor. Your eye contains a retina, a particular light-sensitive screen that collects images. 5. The Focus System: In cameras, we can adjust the focus manually or automatically. The ciliary muscles in your eyes do this instantly. They change the lens to allow you to view both your book and the stars. 6. The Brain as a Memory Card: Just like a camera stores photographs on a memory card, your optic nerve transports image information to the brain, where they are stored and processed. Check out related Question-Answers: Visit QnA.Gyanora.in or NEAR POINT OR LEAST DISTANCE OF DISTINCT VISION -The near point of the human eye is the shortest distance at which an item can be clearly perceived without effort. -It is also known as the minimum distance of clear eyesight. -The near point for a normal healthy adult is about 25 cm away. -Objects closer than 25 cm appear blurred because the eye lens is unable to correctly focus light on the retina. -At the nearest point: -Symbolically, D = 25 cm. *Accommodation of the Eye: Check out related Question-Answers: Visit QnA.Gyanora.in or DEFECT OF VISION AND CORRECTION 1.MYOPIA (Near Sightedness) –Myopia, also referred to as near sightedness, is a vision condition in which a person is able to see nearby object but distant objects appear blurry. –The eye lens focusses light in front of the retina rather than onto it. –causes: It happens because of: -Correction: 2.HYPERMETROPIA (Far Sightedness) -Hypermetropia, also referred to as far sightedness, is an eye disorder that causes a person to view far objects clearly but near objects to appear blurry. -The eye lens directs light behind the retina rather than onto it. -Causes: It happens because of: –Correction: 3.PRESBYOPIA –Presbyopia is an age-related vision condition in which the eye loses the capacity to focus on nearby objects. -Cause: -Symptoms: -Correction: Check out related Question-Answers: Visit QnA.Gyanora.in or ADVANTAGES OF THE EYE IN FRONT OF THE FACE 1. Binocular vision: 2. Improved Depth Perception: 3. Wide Range of Vision: 4. Protection and coordination: REFRACTION THROUGH A PRISM *What is a Prism? *Refraction through a Prism *Angle of Deviation (δ) DISPERSION OF WHITE LIGHT -The process by which white light breaks into its individual colours as it travels through a prism or any other refracting material is known as dispersion. -The spectrum’s seven colours are VIBGYOR à violet, indigo, blue, green, yellow, orange, and red. -Why Does Dispersion Happen? *Recombination of the Spectrum of White Light –After dispersion, the seven colours of white light can be combined again to form white light. This process is called recombination of the spectrum. -Isaac Newton first showed recombination using two prisms: -Observations: TOTAL INTERNAL REFLECTION Total Internal Reflection is the phenomenon in which a light ray, traveling from a denser medium to a rarer medium, is completely reflected back into the denser medium at the boundary, instead of refracting out. -Conditions for TIR: TIR occurs only when both requirements are met. -TIR is used in: *HOW IS RAINBOW FORMED Rainbow is formed due to the combined effect of:Refraction + Dispersion + Internal Reflection 1. The presence of raindrops 2. Refraction and Dispersion 3. Internal Reflection 4. Emergence (Refraction Again) 5. Rainbow Formation ATMOSPHERIC REFRACTION -Atmospheric refraction refers to the bending of light as it passes through the Earth’s atmosphere, which is made up of layers of varied density. -Air’s refractive index varies with temperature and pressure, leading to this phenomenon. -The atmosphere is composed of multiple layers of air with different densities. -Light from a distant object bends gradually as it travels through these layers. 1. Twinkling of Stars -Stars are far away and appear as point sources of light. -Starlight passes through the Earth’s atmosphere, which has uneven air layers of various densities. -Because of atmospheric refraction, the path of starlight is always shifting. -The star’s apparent position and brightness fluctuate, giving the appearance of twinkling. # Why Planets Don’t Twinkle 2. Stars’ Apparent Position -The real position of a star is different from where we see it in the sky. -This happens because of atmospheric refraction -Starlight passes through the Earth’s atmosphere, which has layers of air with different densities. -As light bends continuously towards the normal while moving from rarer to denser layers, the star appears slightly higher than its actual position. 3. Advance Sunrise and Delayed Sunset -We see the Sun earlier than its actual rise and longer after its actual set. -This is due…
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