Everyday Science

Reverse osmosis is a widely used method for water purification, where water is forced through a semipermeable membrane to remove impurities. Osmosis, cytolysis, and turgor pressure are biological or physical processes not used for purifying water.

The ocean appears blue primarily because water absorbs colors in the red part of the light spectrum more strongly than blue. Blue light is scattered and reflected back to our eyes by water molecules and tiny particles in the water. This scattering of blue light within the water is the main reason the ocean looks blue, not just reflection from the surface. Reflection of the sky can contribute but is not the primary cause.

Photolysis is the process of splitting water molecules using light energy, typically occurring in photosynthesis. This distinguishes it from electrolysis (using electric current), radiolysis (using radiation), and thermolysis (using heat).

A transistor amplifies weak electrical signals into stronger signals, making option B correct. It is commonly used as an amplifier in electronic circuits.

A photometer is an instrument used to measure the intensity or brightness of light. Therefore, option B, 'Measuring light Intensity,' correctly describes the function of a photometer.

Astigmatism is a refractive error caused by an irregular curvature of the cornea or lens, which is corrected using cylindrical lenses that compensate for the uneven curvature. Concave, convex, and spherical lenses do not specifically correct astigmatism.

Sonography uses ultrasonic waves, which are sound waves with frequencies higher than the audible range for humans. These waves penetrate the body and reflect off tissues to create images, making option A correct.

Ethyl Mercaptan is commonly added to LPG cylinders because of its strong, distinctive smell, which helps in detecting gas leaks safely and effectively.

Selenium is a non-metal that exhibits semiconducting properties, meaning it can conduct electricity better than typical poor conductors like sulphur, bromine, and phosphorus, which are generally electrical insulators. Therefore, selenium is the correct answer as it is not a poor conductor of electricity among the options.

The Tyndall effect refers to the scattering of light by particles in a colloid or in very fine suspensions. This scattering makes the path of the light visible, which is why option C, scattering, is correct.