What type of radar is used to measure speed based on the Doppler effect?

The choice is Doppler Radar because this type of radar specifically utilizes the Doppler effect to measure the speed of objects. The Doppler effect refers to the change in frequency or wavelength of waves in relation to an observer moving relative to the source of the waves. In the context of radar, when the radar emits a signal that reflects off a moving target, the frequency of the returned signal changes due to the target's motion. By analyzing this frequency change, Doppler Radar can accurately calculate the speed of the object.

Other options do not focus on speed measurement via the Doppler effect. Infrared Radar operates on different principles related to detecting heat or thermal radiation. LiDAR, or Light Detection and Ranging, uses laser light to measure distances and can create precise maps but is not primarily focused on speed measurement based on the Doppler effect. Millimeter Wave Radar utilizes different radio frequencies for applications like imaging and sensing but does not inherently measure speed through the Doppler mechanism. Thus, Doppler Radar stands distinct for its ability to accurately assess speed through the Doppler effect.