The wavelength of an object will appear shorter as it moves toward you. This is because the object is compressing the waves in front of it and stretching the waves behind it. This phenomenon is called the Doppler effect.

The amount that the wavelength changes is proportional to the speed of the object and the angle at which it is moving. The faster the object is moving, the greater the change in wavelength. And the closer the object is to being directly in front of you, the greater the change in wavelength.

The Doppler effect is used in a variety of applications, such as radar, sonar, and astronomy. In radar, the Doppler effect is used to measure the speed of moving objects, such as cars and airplanes. In sonar, the Doppler effect is used to measure the speed of underwater objects, such as submarines and fish. In astronomy, the Doppler effect is used to measure the speed of stars and galaxies.