Question:

Select the correct pair amongst the following.

Updated On: Jul 28, 2022

Spring wood - light colour, high density
Spring wood - dark colour, low density
Autumn wood - light colour, high density
Autumn wood - dark colour, high density

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The Correct Option is D

Solution and Explanation

The yearly growth of secondary xylem is distinct in the area which experiences two seasons, one favourable (spring or rainy season) and the other unfavourable (autumn, winter and dry summer). The wood formed in a single year consists of two types of wood, spring wood and autumn wood. The spring or early wood is much wider than the autumn or late wood. It is lighter in colour and of lower density. Spring wood consists of larger and wider xylem elements. The autumn or late wood is dark coloured and of higher density. It contains compactly arranged smaller and narrower elements which have comparatively thicker walls. In autumn wood, tracheids and fibres are more abundant than those found in the spring wood.

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List II	List II
A. Osmosis	I. Solvent molecules pass through semi permeable membrane towards solvent side.
B. Reverse osmosis	II. Movement of charged colloidal particles under the influence of applied electric potential towards oppositely charged electrodes.
C. Electro osmosis	III. Solvent molecules pass through semi permeable membrane towards solution side.
D. Electrophoresis	IV. Dispersion medium moves in an electric field.

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Concepts Used:

Classification of Colloids

Based on the Nature of Interaction Between Dispersed Phase and Dispersion Medium:

Hydrophilic colloids: These are water-loving colloids. The colloid particles are attracted to the water. They are also known as reversible sols. Examples include Agar, gelatin, pectin, etc
Hydrophobic colloids: These are the opposite in nature to hydrophilic colloids. The colloid particles are repelled by water. They are also called irreversible sols. Examples include Gold sols, clay particles, etc

Based on Type of Particles of Dispersed Phase:

Multimolecular Colloids: A large number of smaller molecules of a substance add on together on mixing and form species that are in the colloidal range.
Macromolecular Colloids: In this colloid, the macromolecule forms a solution with a solvent. The size of particles remains in the range of colloidal particle size. Here, the colloidal particles are macromolecules having a very large molecular mass.
Associated Colloids: Few substances react as strong electrolytes when they are in low concentration, but act as colloidal sols when they are in high concentration. In high concentration, particles aggregate and show colloidal behaviour and these particles are known as the micelles. They are also known as associated colloids. The formation of micelles occurs above a certain temperature and specific concentration. These colloids can be reverted by diluting it.