Understanding Analogies and Measurement Instruments

The question asks us to find the missing word based on the relationship between the first two words. This type of question is an analogy, where the relationship between the first pair of words is the same as the relationship between the second pair.

Let's analyze the first pair:

• TEMPERATURE : THERMOMETER

In this pair, TEMPERATURE is a physical quantity, and THERMOMETER is the instrument used to measure it. A thermometer is specifically designed to quantify how hot or cold something is, which is its temperature.

Now let's look at the second pair and the missing word:

• SOLAR RADIATION : ______

Following the same relationship, we need to find the instrument that measures SOLAR RADIATION. Solar radiation is the radiant energy emitted by the sun.

Let's examine the given options to identify which instrument measures solar radiation:

• A. ANEMOMETER: An anemometer is an instrument used to measure wind speed or velocity. This is not related to solar radiation.
• B. HYGROMETER: A hygrometer is an instrument used for measuring the humidity or amount of water vapor in the air. This is not related to solar radiation.
• C. THERMOPILE PYRANOMETER: A pyranometer is a type of actinometer used for measuring broadband solar radiation flux density (\(W/m^2\)) from a hemispherical field of view. A thermopile pyranometer uses a thermopile sensor to measure the solar radiation. This instrument directly measures solar radiation.
• D. SPHYGMOMANOMETER: A sphygmomanometer is a medical device used to measure blood pressure. This is not related to solar radiation.

Based on the analysis of the instruments, the instrument used to measure SOLAR RADIATION is the THERMOPILE PYRANOMETER.

Therefore, the analogy is:

TEMPERATURE : THERMOMETER :: SOLAR RADIATION : THERMOPILE PYRANOMETER

Let's summarize the relationship:

Analyzing Options for Solar Radiation Measurement

Let's quickly review what each option measures to confirm our choice for SOLAR RADIATION:

• ANEMOMETER: Measures wind speed.
• HYGROMETER: Measures humidity.
• THERMOPILE PYRANOMETER: Measures solar radiation.
• SPHYGMOMANOMETER: Measures blood pressure.

Clearly, the THERMOPILE PYRANOMETER is the instrument designed to measure SOLAR RADIATION.

The missing word is THERMOPILE PYRANOMETER, which corresponds to Option C.

Revision Table: Measurement Instruments

Additional Information on Solar Radiation and Measurement

Solar radiation is a fundamental component of the Earth's energy balance and plays a crucial role in climate, weather patterns, and renewable energy (solar power). Measuring solar radiation accurately is important for various applications, including meteorology, climate research, agriculture, and solar energy system design and monitoring.

Different types of instruments measure different aspects of solar radiation:

• Pyranometer: Measures global solar radiation (direct and diffuse radiation from the sky) on a horizontal surface. Thermopile pyranometers are common types.
• Pyrheliometer: Measures direct normal solar radiation, requiring tracking the sun's position.
• Pyrgeometer: Measures terrestrial longwave radiation (infrared radiation emitted by the Earth's surface and atmosphere).

The THERMOPILE PYRANOMETER measures the total solar radiation received over a wide spectrum, making it the appropriate instrument for the analogy related to measuring SOLAR RADIATION generally.