Physics Measuring Instruments

Altimeter setting adjusts the barometric pressure scale so the altimeter indicates true altitude at field elevation. True altitude is the actual height above mean sea level under current atmospheric conditions. Answer B is correct - the alteter setting calibrates the instrument to read true altitude at the airport's elevation. Absolute altitude (A) is height above ground level. Calibrated altitude (C) is indicated altitude corrected for instrument error. Answer D describes pressure altitude, not the purpose of altimeter setting.

The Attitude Indicator (also called Artificial Horizon) displays the aircraft's orientation relative to the earth's horizon, showing pitch (nose up/down) and roll (bank angle). This directly gives pitch information. The VSI shows vertical speed rate, not absolute pitch. Ground Speed Indicator shows horizontal speed over ground. Altimeter shows altitude, not pitch angle.

EEG (electroencephalogram) records brain electrical activity and can identify REM sleep patterns, which is when most dreaming occurs. ECG measures heart activity, PGO waves are specific neural patterns (not an instrument), and REM is a sleep stage, not a measurement tool.

Seismographs are specifically designed to detect and record seismic waves during earthquakes. Barographs track atmospheric pressure, hydrographs measure water levels, and pantographs are mechanical devices for copying drawings.

The correct spelling is 'gauge' with 'au' in the middle. This word is an exception to common patterns and doesn't follow the 'au' sound rule consistently. Options A, C, and D are all misspellings.

An angstrom (A) is a unit of length equal to 10^-10 meters or 0.1 nanometers, commonly used to measure the wavelength of light and atomic-scale distances. While it can measure any small length, its most common application is for electromagnetic waves, including visible light.

A sextant is a navigation instrument used to measure the angle between a celestial object (like the sun or stars) and the horizon, allowing sailors to determine their latitude at sea.

Troy weight is a traditional system of mass measurement used specifically for precious metals like gold, silver, and platinum. It originated in medieval England and is distinct from avoirdupois weight used for general goods. Liquids are measured by volume, fossil fuels by various weight systems, and medicines use apothecary or metric systems.

A barometer is a scientific instrument used to measure atmospheric pressure. It helps in weather forecasting as pressure changes indicate approaching weather systems. Other options measure different quantities - hygrometer (humidity), flowmeter (flow rate), thermometer (temperature).

A hygrometer is the scientific instrument specifically designed to measure relative humidity in the atmosphere. A barometer measures air pressure, while a thermometer measures temperature. 'Humidmeter' is not a standard scientific instrument.

An ammeter (from 'ampere-meter') measures electric current in amperes. Electromagnetic fields are measured by gaussmeters. Light intensity is measured by photometers or lux meters. Loudness is measured in decibels using sound level meters.

A seismograph is the scientific instrument that measures and records the intensity, direction, and duration of seismic waves from earthquakes. The prefix 'seismo-' comes from Greek for earthquake.

The Fujita scale (F-Scale) is used to rate the intensity of a tornado based on the damage it inflicts on human-built structures and vegetation. It was later updated to the Enhanced Fujita (EF) scale.

An odometer is the instrument in a vehicle used to measure the total distance traveled. A speedometer measures instantaneous speed, a thermometer measures temperature, and a differential pinion is a mechanical gear component.

A speedometer is the instrument that shows the speed of a vehicle. The word 'Speed-O-meter' is a playful spelling of speedometer. The other options (Speed A meter, Speed M meter, Speed Z meter) are fictional devices.