Which of the following factors determines the colour of scattered light in the atmosphere, according to the T… - RRB Nsg. Superintendent - 29 April 2025 (Shift-3rd)

RRB Nsg. Superintendent - 29 April 2025 (Shift-3rd)

General Knowledge

Easy

Appeared in: RRB Nsg. Superintendent - 29 April 2025 (Shift-3rd)

Explanation

The Tyndall effect is the scattering of a light beam by particles in a colloid or suspension.
The color of the scattered light depends on the size of the scattering particles relative to the wavelength of the light.
Very small particles (smaller than the light's wavelength) scatter shorter wavelengths, like blue and violet, more effectively.
Larger particles (bigger than the light's wavelength) scatter all wavelengths of light more equally, which makes the scattered light appear white.

Option A: The color of the scattered light is due to the physical phenomenon of scattering, which depends on particle size, not the inherent color of the particle itself.
Option B: This statement is fundamentally false. The Tyndall effect is defined by the interaction between light and the scattering particles. Without the particles, there is no scattering.
Option D: The density of the particles (i.e., the number of particles per unit volume) influences the intensity or total amount of scattered light, making the effect more or less visible. It does not, however, determine the color of the scattered light.

Visual 1: Diagram - A diagram illustrating the Tyndall effect, showing a light beam passing through a true solution (no scattering) and a colloid (visible scattered beam).
Visual 2: Infographic - An infographic comparing Rayleigh scattering (small particles, blue light) with Mie scattering (larger particles, white light) with examples like the blue sky and white clouds.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Physics of light scattering (Tyndall effect) as background academic context rather than a clinical decision trigger.
The Tyndall effect has applications in laboratory medicine to determine the amount of turbidity (cloudiness) in a sample, such as in nephelometry, which measures the concentration of suspended proteins like immunoglobulins.
In ophthalmology, a slit lamp is used to shine a beam of light into the eye. The presence of a Tyndall effect (called 'flare') in the anterior chamber indicates that proteins have leaked from blood vessels, a sign of inflammation (uveitis).
What if? - If the particles were all of a uniform size that was optimal for scattering red light, the scattered light would appear reddish instead of blue. This principle is used in some specialized analytical techniques.

How to Approach the Question

First, identify the core scientific principle in the question, which is the 'Tyndall effect'.
Recall the definition of the Tyndall effect: the scattering of light by particles in a colloid or suspension.
Analyze the specific question: what 'determines the colour' of the scattered light?
Evaluate the relationship between light properties (wavelength) and particle properties. Remember that scattering phenomena are highly dependent on the size of the particle relative to the wavelength of the light.
Eliminate the other options. The particle's own color is irrelevant to the physics of scattering. The particle's existence is necessary, so 'does not depend' is wrong. Density affects intensity, not color.
Conclude that the size of the scattering particle is the correct factor that determines the color.

Concept Tested & Keywords

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