Which of the following is an example of active remote sensing?

Active remote sensing involves the use of instruments that emit their own energy to collect data about the Earth's surface. This is in contrast to passive remote sensing, which relies on naturally occurring energy, such as sunlight.

The correct answer, which includes radar and LiDAR, exemplifies active remote sensing because both technologies send out their own signals—radar emits microwaves, while LiDAR emits laser pulses. These systems measure the time it takes for the emitted signal to bounce back after striking an object, allowing them to create detailed images or maps of the surface.

In contrast, the other options do not represent active remote sensing. A satellite capturing sunlight reflects the principle of passive remote sensing, as it depends on natural sunlight rather than emitting its own signals. An infrared camera recording images at night typically relies on thermal radiation emitted by objects, which is also a form of passive sensing. Finally, using weather balloons to measure temperature involves collecting data from the atmosphere without actively sending signals into it, again aligning with passive methodologies. Thus, radar and LiDAR are distinct in that they actively probe the environment, making them prime examples of active remote sensing technologies.