What kind of thermometer is inserted in a water bath to the point where the "immersion line" meets the level of the water?

The correct answer is a partial immersion thermometer. This type of thermometer is specifically designed to be inserted into a liquid, but only to a designated point, known as the immersion line. This ensures that the sensitive portion of the thermometer is adequately submerged in the liquid while keeping the upper part, where the reading is observed, above the liquid level to avoid damage or interference.

In many laboratory settings, particularly in the context of measuring water temperatures in baths, it is crucial to use a thermometer that can accurately measure the temperature of the liquid without over-immersion, which could lead to inaccurate readings or damage to the instrument.

Digital thermometers and glass thermometers, while useful for various applications, are not specifically designed for partial immersion in the manner described. Digital thermometers are often used for a broad range of temperature measurements, while glass thermometers may require complete immersion for accuracy. A maximum thermometer, on the other hand, is calibrated to indicate the highest temperature reached and may not be suitable for direct immersion in applications like those involving a water bath.