Here's why:
* Waves and Frequency: Think of waves as a series of crests and troughs. The frequency of a wave is how many crests pass a point in a given time. Higher frequency means more crests passing by per second.
* Moving Source: When the source of the waves (like a moving object) is approaching you, the crests are being compressed together. This means more crests pass you in a given time, increasing the frequency.
* Wavelength and Frequency: Wavelength is the distance between two consecutive crests. Since frequency and wavelength are inversely proportional (higher frequency means shorter wavelength), a higher frequency leads to a shorter wavelength.
In summary: As an object moves towards you, its wavelength decreases because the wave crests are compressed, leading to a higher frequency.
