Science [2 Mark Questions]

We rarely use concave lens as is usually supposed. We often use convexo concave lens or any other diverging lens.

Ozone is a form of oxygen. It is formed by three atoms of oxygen (Os), whereas normal oxygen molecule is diatomic (02). Oxygen is essential for all aerobic forms of life and for combustion activities. Ozone, is a deadly poison. Very little of it is present in lower part of the atmosphere called troposphere. In the stratosphere, ozone layer comprises high concentration of ozone some 18-26 km above. Ozone performs an essential function. It shields the surface of the earth from the harmful ultraviolet (UV) radiation of the sun.

Many insecticides such as aldicarb, aldrin, chlorodane and dieldrin with many others have been banned in India due to their harmful effects on life. These pesticides are non-biodegradable and get accumulated in the body of organisms and the concentration of these chemicals increases with each trophic level, thus, killing a large number of organisms and putting various health risks to others.

The two phases of photosynthesis reactions are as follows:
a) Light reaction; In light-dependent reactions, the energy from sunlight is absorbed by chlorophyll and converted into chemical energy in the form of electron carrier molecules like ATP and NADPH. It takes place in the thylakoid of the grana of the chloroplasts.
b) Dark reaction: In light-independent reactions (Calvin Cycle), carbohydrate molecules are assembled from carbon dioxide using the chemical energy harvested during the light-dependent reactions. It takes place in the stroma of the chloroplasts.

Components of the transport system in plants
1. Xylem tissue - Vessels and tracheoles of roots, stems and leaves are concerned with transport of water and minerals.
2. Phloem transports food, amino acid and other substances.

Pollination is the act of transferring pollen grains from the male anther of a flower to the female stigma. The goal of every living organism, including plants, is to create offspring for the next generation. One of the ways that plants can produce offspring is by making seeds. Seeds contain the genetic information to produce a new plant.
Self-pollination:
i. It is the transfer of pollen grains from the anther of the stamen to the stigma of the carpel of the same flower or different flower of the same plant.
ii. It does not require external agents.
iii. It does not introduce variation,
iv. It is a sure and economical method.
v. It avoids mixing or dilution of the original characters.
vi. The progeny becomes weaker after every generation
Cross-pollination:
i. It is the transfer of pollen grains from the anther to the stigma of different flowers of different plants.
ii. It requires external agents like wind, insects, etc. to carry out pollination.
iii. It introduces variation and adaptability.
iv. It is not economical and is highly wasteful.
v. Good characters of a race can be diluted.
vi. The progeny becomes healthier and better fitted for existence.

Soaps are sodium or potassium salts of long chain fatty acids. The action of a soap is based on the presence of both hydrophil and hydrophobic groups in a soap molecule. This action emulsifies the oily dirt and helps in its removal.
The two ends of a soap molecule have different properties. When soap is added to water, the ionic, hydrophilic end of soa molecule dissolves in water. The hydrocarbon chain of soap molecule is hydrophobic and it dissolves in hydrocarbons i.e. linl with oily dirt. The hydrocarbon chain of soap molecule orients towards the oil droplet while the ionic end orients towards wat (polar solvent). This is how, soap molecules form structures called micelles where the oily dirt is collected in the centre. Thu soap micelles help in dissolving dirt in water. Micelles stay in solution as colloids and the dirt suspended in the micelles is easil rinsed away.
Micelle formation will not take place in a solvent like ethanol because ethanol will dissolve the hydrocarbon chain of a soc molecule also.