If an aeroplane approaches a radar system, then the wavelength of the communication wave reflected from the aeroplane to the ground station would

Explanation

* Doppler Effect Principle: The Doppler Effect describes the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave's source. When a source of waves moves towards an observer, the waves are compressed, leading to a decrease in wavelength and an increase in frequency. Conversely, if the source is moving away, the waves are stretched, resulting in an increased wavelength and decreased frequency. This applies to all types of waves, including the electromagnetic waves used in radar systems. * Application to the Scenario: In this case, the aeroplane is approaching the radar system. The radar emits a wave, which is reflected by the aeroplane. From the perspective of the ground station receiving the reflected wave, the aeroplane acts as a moving source of that reflected wave. Since the aeroplane is moving towards the ground station, the reflected waves are compressed, causing their wavelength to become shorter.