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

4 Marks

SAQ-1 : What happens if dispersion and scattering of light do not occur ?

Introduction

Scattering and dispersion are two fundamental phenomena related to the behavior of light when it interacts with matter. But have you ever wondered what our world would look like if these processes never occurred? Let’s delve into that hypothetical scenario.

The World Without Dispersion and Scattering:

White Sun:

1. Role of Dispersion and Scattering:
   Dispersion and scattering give the sun its familiar warm hues during sunrise and sunset.
2. Sun Appearance Without These Phenomena:
   Without these phenomena, the sun would appear consistently white throughout the day.
3. Impact on Sunrise and Sunset Colors:
   Lacking the spectacular hues of red, orange, and pink during dawn and dusk.

A Black Sky and Oceans:

1. Cause of the Blue Sky:
   The beautiful blue sky owes its color to the scattering of sunlight by atmospheric particles.
2. Reason for Blue Color:
   Specifically, the blue light scatters more than other colors because of its shorter wavelength.
3. Sky Appearance Without Scattering:
   Without scattering, the sky wouldn’t appear blue. Instead, it would be black, much like space.
4. Effect on Ocean Color:
   Similarly, oceans reflect the sky’s color, so they too would appear black rather than blue.

No Rainbows:

1. Origin of Rainbows:
   Rainbows result from the dispersion of sunlight by water droplets in the atmosphere.
2. Process of Color Separation:
   Each color in the sunlight bends by a slightly different amount when it passes through the water droplets, leading to the separation of colors that we see in a rainbow.
3. Rainbow Absence Without Dispersion:
   Without dispersion, this beautiful natural arc of colors would be non-existent.

Summary:

The phenomena of dispersion and scattering play crucial roles in crafting the vivid and varied colors we observe in our environment. Their absence would dramatically alter our perception of the world, making it appear vastly different and arguably less enchanting. It underscores the significance of these seemingly simple processes in creating the vibrant world we see around us.

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SAQ-2 : What happens, if ciliary muscles do not perform contraction and expansion ? Guess and write.

Introduction

Ciliary muscles in our eyes play a critical role in focusing on objects at varying distances. Let’s discuss what would happen if these muscles lost their ability to contract and expand.

The Significance of Ciliary Muscles:

1. Role in Focusing:
   Ciliary muscles control the shape of the eye’s lens. When these muscles contract, the lens becomes thicker, allowing us to focus on nearby objects. Conversely, when they relax, the lens becomes thinner, enabling us to focus on distant objects.
2. Loss of Accommodation:
   If ciliary muscles couldn’t contract or expand, our eyes would lose their ability to adjust the lens’s shape. This phenomenon is called ‘accommodation‘. As a result, our eyes would be stuck in a fixed focus, either for distant or near objects, depending on the default state of the lens.
3. Potential for Eye Strain and Fatigue:
   Without the flexibility provided by ciliary muscles, our eyes would constantly strain to bring objects into focus, leading to discomfort, headaches, and rapid eye fatigue.
4. Incorrect Assumption about Damage:
   Contrary to the idea that more light would enter the eye and cause damage, the contraction and expansion of ciliary muscles do not control the amount of light entering the eye. That role belongs to the iris and the pupil. The ciliary muscles’ primary function is related to focus, not light regulation.

Summary

The proper functioning of ciliary muscles is vital for clear vision across different distances. Their malfunction would severely limit our visual adaptability, leading to significant discomfort and potential vision issues. It’s essential to note that while these muscles are crucial for focus, they don’t play a role in regulating the amount of light entering our eyes.

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SAQ-3 : What is the cause of presbyopia?

Introduction

Presbyopia is a common vision condition that affects people, usually starting in the late 30s or early 40s. It’s characterized by a difficulty in focusing on close-up objects. Let’s delve into the causes behind it.

Understanding Presbyopia:

1. Ageing Factor:
   As we age, the lens inside our eye gradually loses its flexibility, making it harder to change its shape and thus focus on objects that are close.
2. Weakening of Ciliary Muscles:
   The ciliary muscles, responsible for changing the shape of the lens to focus on different distances, lose their strength and elasticity over time. As they weaken, their ability to help the lens focus effectively diminishes.
3. Loss of Lens Elasticity:
   The lens in our eye is made of a flexible material that changes shape to focus on objects at various distances. With age, this flexibility decreases, and the lens becomes stiffer. A stiffer lens can’t adjust its shape as easily, which is essential for near vision.
4. Difference from Other Vision Issues:
   It’s important to distinguish presbyopia from other refractive errors like myopia, hyperopia, and astigmatism. While all these conditions relate to how the eye focuses light, their causes and treatments differ. Presbyopia specifically stems from the natural ageing process.

Summary

Presbyopia is an inevitable consequence of the ageing process that affects the eye’s lens and ciliary muscles. It results in decreased near vision, making activities like reading or sewing more challenging without corrective lenses. Understanding its causes can help individuals be better prepared for its onset and seek appropriate interventions.