Which type of sensor can measure the distance to an object using electromagnetic waves?

An active sensor is designed to emit its own signals and then measure the reflections of those signals to determine the distance to an object. This operational principle relies on the use of electromagnetic waves, which the sensor sends out. The time it takes for the waves to bounce back to the sensor after hitting an object is measured, and from this, the distance can be calculated.

This characteristic sets active sensors apart from passive sensors, which only detect signals that are naturally emitted or reflected from objects, such as sunlight. Optical sensors are a specific type of sensor that may also operate in a passive or active manner; however, they typically rely on visible light rather than a broader range of electromagnetic waves. Radar sensors fall under the category of active sensors, as they specifically utilize radio waves to measure distances, making them effective in various environments, including poor visibility conditions.

In summary, the reason an active sensor is the correct answer is that it specifically performs the function of measuring distances by emitting and detecting electromagnetic waves, which is integral for applications like distance measurement to objects.