Match the names of scientific instruments in Column I with their designated fields of applications in Column II and select the correct answer using the options given below the columns: Column I A. Galvanometer B. Hygrometer C. Manometer D. Tonometer Column II 1. Measure internal pressure of the eye 2. Measure electric currents 3. Measure humidity levels 4. Pressure of gases

Galvanometer

• A galvanometer is mainly used in various electrical circuits for detecting current as well as in experiments to decide the null point.
• If a heavy current flows through the coil in the galvanometer, then the pointer in this may strike the stop pin because of a very large deflection.
• The SI unit of the figure of merit of the galvanometer is Ampere per division.

Hygrometer

• A hygrometer is an instrument used to measure the amount of water vapour in the air, in soil, or in confined spaces.
• Humidity is the measure of the amount of moisture in the air.
• Hygrometer works on the phenomenon called evaporative cooling.
• When water evaporates from any surface, it becomes cool because water molecules take heat energy from the surface during evaporation.
• Due to this cooling effect wet bulb always shows low temperature than a dry bulb.

Manometer

• Manometers are devices used for measuring the pressure at a point in a fluid, by balancing the column of fluid by the same or another column of fluid.
• The most common form of the manometer is the conventional mercury barometer used to measure atmospheric pressure.

Tonometer

• A tonometer is an instrument that determines intraocular pressure by measuring the resistance of your cornea to indentation.
• Tonometry is a test to measure the pressure inside your eyes.
• The test is used to screen for glaucoma and to measure how well glaucoma treatment is working.
• People over age 40 years, particularly African Americans, have the highest risk for developing glaucoma.
• Regular eye exams can help detect glaucoma early. Hence, Option 2 is correct.