Question

Tails of comets are comets are visible due to:
A.Tyndall effect
B.Reflection
C.Brownian movement
D.None of these

Answer 1

We have to know that the tails look as the comet approaches the Sun. Sunlight pushes on things, but in a gentle way. Because the dust particles of comets are very small, they are pushed away from the Sun into a long tail.

Complete step by step answer:
As comets come near to the Sun, tails of dust and ionized gas are developed. Comets contain two tails, a dust tail and a plasma tail. The dust tail looks whitish-yellow as it comprises tiny particles, about the smoke particles size which reflect sunlight. Tail of comets appears as a Tyndall cone because of the scattering of light by the tiny solid particles that are left behind by the comet in its route.
We can define the Tyndall effect as the phenomenon of scattering of particles of light in its path. When a beam of sunlight enters into the dusty window through the window, then its path becomes visible to us. We have to know the effect of scattering of light in colloidal dispersion, while displaying no light in a true solution is known as Tyndall effect. We can use this effect to determine if a mixture is a true solution or a colloid.
Therefore, the option (A) is correct
We can say reflection is a spot in a diffraction pattern.
Therefore, the option (B) is incorrect.
Colloidal particles that are present in a colloidal solution show a vital property called the Brownian movement. We can define Brownian movement as the uninterrupted zigzag movement of the colloidal particles in the dispersion medium present in a colloidal solution. We can say Brownian movement is due to the unequal bombardment of the moving molecules of dispersion medium on colloidal particles. The moving molecules of the dispersion medium strike on colloidal particles from all sides and transfer momentum to them.
Therefore, the option (C) is incorrect.

Therefore, the option (A) is correct.

Note:
We must remember that the Brownian movement plays a vital role in imparting stability to a sol. This is because the Brownian movement opposes the gravitational forces that act on colloidal particles and prevent them from getting settled down.