4 Most FAQ’s of Human Eye and Colourful World Chapter in Class 10th Physical Science (TS/AP)

8 Marks

LAQ-1 : Answer the following questions from the above information

1.What is the defect of vision in D suffering from? Why does it happen?

2.Whose defect of vision can be corrected by using biconcave lens?

3.Who is suffering with similar defect of vision as of B?

4.Who among the above do not have any defect of vision?

Introduction

The passage presents information about the vision defects of various individuals and the solutions to rectify them. We will now answer some specific questions based on this information.

Identifying D’s Vision Defect:

1. Defect: D suffers from Presbyopia.
2. Cause: Presbyopia arises due to the natural aging process. As individuals age, the eye’s lens becomes less flexible, causing difficulty in reading up close. This diminishing flexibility is attributed to weakening ciliary muscles and a decrease in the power of accommodation of the eyes.

Purpose of Bi-concave Lens:

Correction: A biconcave lens is used to correct the vision defect of person ‘A’.

Identifying Similar Vision Defects:

Similar Defect: Both person ‘B’ and person ‘C’ suffer from the same vision defect.

The Person without Vision Defect:

Clear Vision: Person ‘E’ is the individual who does not suffer from any vision defect.

Summary

In the provided information, various individuals suffer from different vision defects. D has Presbyopia, which is due to age-related changes in the eye. The vision defect of A can be corrected using a biconcave lens. Both B and C have the same vision defect, while E has no vision defect.

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LAQ-2 : Mention the required material and chemicals for the experiment of “Scattering of light.” Write the experimental procedure.

Introduction

The phenomenon of “Scattering of Light” is an essential concept in optics. Through a simple experiment using chemicals and everyday materials, we can observe this fascinating occurrence.

Required Materials and Chemicals:

1. Beakers: To hold the chemical solution.
2. Sodium Thiosulphate (Hypo): A chemical that reacts with sulphuric acid.
3. Sulphuric Acid: To induce the chemical reaction.
4. Water: As a solvent.

Experimental Procedure:

1. Preparation: Mix a solution of sodium thiosulphate (hypo) with sulphuric acid in a glass beaker.
2. Observation of Sulphur Formation: Monitor the formation of Sulphur grains in the solution.
3. Exposure to Sunlight: Place the reacting beaker in a location with abundant sunlight to observe the reaction clearly.
4. Tracking Changes: Keep an eye on the changes happening within the beaker, especially the Sulphur precipitates.
5. Initial Appearance: Initially, Sulphur grains are small and appear blue due to their size being comparable to the wavelength of blue light.
6. Progression of the Reaction:
   • As the reaction progresses, the size of the Sulphur grains increases.
   • Their color transitions from blue to white as their size grows and they start scattering light of other wavelengths.
7. Understanding the Result:
   • At the outset, the small size of the Sulphur grains scatters predominantly blue light.
   • As they grow larger, they scatter a combination of colors, resulting in a white appearance.

Summary

The experiment on the scattering of light using sulphur grains showcases how the size of particles affects the colors they scatter. Initially, blue light is scattered due to smaller particles, but as they grow, they scatter all colors resulting in white. This offers a hands-on understanding of the principles behind the scattering of light.

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LAQ-3 : How do you correct the eye defect myopia ?

Introduction

Myopia, commonly known as near-sightedness, is a prevalent eye defect. Individuals with myopia can see nearby objects clearly but struggle to focus on distant objects. The condition can be effectively corrected using appropriate lenses. This article elucidates how myopia occurs and how it’s corrected.

Understanding Myopia

1. Definition:
   Myopia or near-sightedness is an eye condition where a person can distinctly see nearby objects, but distant objects appear blurry.
2. How the Normal Eye Works:
   Ideally, our eyes form a clear image on the retina when an object is within a particular range, typically between the far point (M) and the least distance of distinct vision (L).

The Myopic Eye

1. Individuals with myopia have a maximum focal length less than the standard 2.5 cm. This means they can’t view objects clearly beyond a certain point, known as the far point.
2. If objects are positioned beyond this range, the light rays, after refraction in the eye lens, converge and form an image in front of the retina instead of on its surface.

Role of Bi-Concave Lenses

1. Myopia can be effectively corrected using a bi-concave lens.
2. The bi-concave lens diverts incoming light rays in such a way that they converge exactly onto the retina, ensuring a clear image.

Working Principle

1. The bi-concave lens creates a virtual image of a distant object at the individual’s far point. Although the object might be at infinity, this virtual image becomes the ‘object‘ for the eye lens.
2. The eye lens then focuses this image onto the retina, ensuring clear vision.

Summary

Myopia is an eye condition that affects one’s ability to see distant objects clearly. By using a bi-concave lens of the appropriate power, the defect can be corrected, enabling the individual to see distant objects as clearly as nearby ones. Proper understanding and timely intervention can ensure optimal vision for those affected.

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LAQ-4 : Explain the formation of rainbow.

Introduction

The rainbow, one of nature’s most beautiful spectacles, has fascinated humans for centuries. While it seems magical, the formation of a rainbow is based on scientific principles involving light. This article breaks down the process behind the phenomenon of the rainbow.

Formation of Rainbow: A Step-by-Step Explanation:

1. Combination of Phenomena: A rainbow’s formation is the result of three critical optical phenomena: dispersion, refraction, and reflection of light.
2. Setting the Scene: Rainbows typically appear in the sky after a rain shower, especially when the sun shines while it’s still raining.
3. Entering the Water Droplets: Sunlight consists of multiple colors, each with its unique wavelength. As sunlight enters individual water droplets present in the atmosphere post-rain, these droplets act as tiny prisms.
4. Dispersion and Refraction: When light passes from one medium to another (from air into the water droplet), it slows down, leading to the bending or refraction of light. Due to the different wavelengths of the various colors, each bends at a slightly different angle, causing them to spread out. This phenomenon is known as dispersion.
5. Internal Reflection: After dispersion, the light reflects internally within the droplet. This reflection makes the light head towards the other side of the droplet.
6. Exiting the Droplet: The dispersed and internally reflected light exits the droplet, undergoing refraction once again. This second refraction further separates the colors, making them more distinct.
7. The Result – VIBGYOR: Due to the combined effects of dispersion, internal reflection, and double refraction, we observe the seven colors of the spectrum in the order of VIBGYOR – violet, indigo, blue, green, yellow, orange, and red.

Summary

Rainbows are a delightful blend of science and art. While they appear mystical and enchanting, understanding the principles of light involved in their formation makes them even more intriguing. They serve as a reminder of how nature can combine simple elements in intricate ways to create breathtaking beauty.