Scientific Instruments — Set 7

Correct Answer: C. Barometer

• **Barometer** = A barometer measures atmospheric pressure; a mercury barometer supports a column of mercury whose height equals the atmospheric pressure. • **Torricelli (1643)** — Evangelista Torricelli invented the mercury barometer in 1643; standard atmospheric pressure is 760 mmHg (101,325 Pa) at sea level. • 💡 Wrong-option analysis: Anemometer: measures wind speed; Manometer: measures pressure of enclosed gases; Altimeter: uses atmospheric pressure to calculate aircraft altitude (a derived instrument).

Correct Answer: D. Pyrometer

• **Pyrometer** = A pyrometer is a non-contact device that measures high surface temperatures remotely by analysing the thermal radiation emitted by the object. • **steel furnaces** — Pyrometers are used in steel plants, glass furnaces, and ceramics kilns to monitor temperatures above 600°C where direct contact is impossible. • 💡 Wrong-option analysis: Thermometer: requires direct contact and works only within a moderate temperature range; Calorimeter: measures heat of chemical reactions in an insulated container; Cryometer: measures very LOW temperatures near absolute zero.

Correct Answer: D. Anemometer

• **Anemometer** = An anemometer measures wind speed (velocity); the cup anemometer is the most common type, where rotating cups spin faster with increasing wind. • **weather stations** — Wind speed data from anemometers is vital for aviation safety, weather forecasting, and wind energy calculations; speed is reported in m/s or knots. • 💡 Wrong-option analysis: Speedometer: measures vehicle speed; Tachometer: measures engine shaft rotation (RPM); Chronometer: measures precise time.

Correct Answer: B. Seismograph

• **Seismograph** = A seismograph detects and records ground motion during earthquakes, producing a seismogram that shows the amplitude and timing of seismic waves. • **Richter scale** — The seismogram output is used to calculate earthquake magnitude on scales like the Richter scale; multiple stations triangulate the epicentre. • 💡 Wrong-option analysis: Barograph: records atmospheric pressure changes over time; Spectrograph: records the spectrum of light or sound; Cardiograph: records heart electrical activity (ECG).

Correct Answer: B. Periscope

• **Periscope** = A periscope uses two plane mirrors (or prisms) set at 45° to redirect light, allowing a person in a low position (trench or submarine) to see objects above. • **45-degree mirrors** — The two mirrors are parallel and each tilted at 45°; used in World War I trenches for safe observation and still used in submarines today. • 💡 Wrong-option analysis: Stroboscope: produces rapid flashes to study fast-rotating objects; Microscope: magnifies small nearby objects, not for seeing over obstacles; Telescope: magnifies distant objects but requires line-of-sight, not redirected viewing.

Correct Answer: B. Galvanometer

• **Galvanometer** = A galvanometer is a highly sensitive electro-mechanical instrument that detects and measures microampere-level currents by deflecting a needle in a magnetic coil. • **Wheatstone bridge** — Used in Wheatstone bridge circuits as a null detector; can be converted to an ammeter (shunt resistor) or voltmeter (series resistor). • 💡 Wrong-option analysis: Ammeter: measures milliamperes to amperes (larger currents); Voltmeter: measures potential difference; Wattmeter: measures electrical power in watts.

Correct Answer: A. Sphygmomanometer

• **Sphygmomanometer** = A sphygmomanometer measures arterial blood pressure using an inflatable arm cuff to occlude the brachial artery and a pressure gauge to read the values. • **mmHg** — Blood pressure is recorded in millimetres of mercury (mmHg); hypertension (high BP) is defined as consistently above 140/90 mmHg. • 💡 Wrong-option analysis: Stethoscope: used alongside sphygmomanometer to hear Korotkoff sounds, but cannot measure pressure alone; ECG Machine: records electrical activity of the heart; Thermometer: measures body temperature.

Correct Answer: B. Earthquake intensity

• **Earthquake intensity** = A seismograph measures the intensity, duration, and direction of seismic waves generated by earthquakes, producing a seismogram. • **Richter / Moment Magnitude** — The seismogram is analysed to assign earthquake magnitude on the Richter or Moment Magnitude Scale; even minor tremors imperceptible to humans are recorded. • 💡 Wrong-option analysis: Wind speed: measured by an anemometer; Atmospheric pressure: measured by a barometer; Humidity: measured by a hygrometer.

Correct Answer: A. Hydrometer

• **Hydrometer** = A hydrometer measures the specific gravity (relative density) of liquids compared to water, based on Archimedes' principle of buoyancy. • **float depth** — A denser liquid pushes the hydrometer higher; used in wine-making, battery acid testing, and antifreeze concentration measurement. • 💡 Wrong-option analysis: Lactometer: a specialised hydrometer used only for milk purity; Manometer: measures gas/liquid pressure in closed containers; Viscometer: measures viscosity (resistance to flow), not density.

Correct Answer: C. Reflection

• **Reflection** = A periscope works on the principle of regular reflection; two plane mirrors placed at 45° to the tube's axis reflect incoming light twice to redirect the line of sight. • **two 45° mirrors** — Each mirror turns the light by 90°; two successive reflections redirect the image upward (or downward), allowing observation from a concealed position. • 💡 Wrong-option analysis: Refraction: bending of light at a boundary between media (lens phenomenon); Total internal reflection: occurs inside glass/water at critical angle (principle of optical fibre); Diffraction: bending of waves around obstacles.