Question

Tyndall effect is produced by:

• A. True solutions of light
• B. Scattering of light
• C. Refraction of light
• D. Movement of particles

Hint:

The Tyndall effect is a result of the scattering of light by particles in colloidal solutions, not by their movement or refraction.

Answer 1

The Correct Option is B

The Tyndall effect is a phenomenon where light is scattered by particles in a colloid or in small particles in a fine suspension. This occurs when the diameter of the particles is in the range of 1 nanometer to 1 micrometer. The effect is named after the 19th-century physicist John Tyndall who first studied it.

Let's explore why the correct answer is "Scattering of light":

• Scattering of light: The Tyndall effect is directly related to the scattering of light. When a beam of light passes through a colloidal solution or a suspension, the particles scatter the light in different directions, making the path of the beam visible. This is the correct explanation for the phenomenon observed in the Tyndall effect.
• True solutions of light: In a true solution, the solute particles are molecular-sized (less than 1 nanometer) and do not scatter light; thus, they do not show the Tyndall effect.
• Refraction of light: Refraction refers to the bending of light as it passes from one medium to another, which is a different phenomenon from scattering.
• Movement of particles: While the movement of particles can cause scattering, the Tyndall effect specifically refers to the scattering aspect rather than the mere movement of particles.

Therefore, the Tyndall effect is characterized by the scattering of light due to the presence of particles in a colloid or a fine suspension.

Answer 2

The Tyndall effect is essentially a description of what happens to light when it passes through a colloid or fine suspension: something happens to the light itself that makes its path visible. Let's check what that "something" actually is among the options.

1. True solutions of light: This phrase does not correspond to a real optical process; true solutions, in fact, do not show this effect at all because their particles are too small to interact with light this way.
2. Scattering of light: When light hits particles roughly its own wavelength in size, it gets redirected in many directions rather than travelling straight through, which is what makes the beam's path visible from the side. This is the process behind the Tyndall effect.
3. Refraction of light: Refraction is the bending of light as it passes from one transparent medium into another (like from air into water), a directional bending, not the sideways redirection of light off small particles.
4. Movement of particles: Particles in a colloid do move (Brownian motion keeps them suspended), but this movement by itself does not make a light beam visible; it is the scattering off the particles, not their motion, that does that.

The visible beam in the Tyndall effect comes from light being redirected off colloidal particles in many directions, which is scattering.

So the correct answer is scattering of light.