If a blinking light source approaches an observer, the observed wavelength of the light will decrease. This phenomenon is known as the Doppler effect.
The Doppler effect occurs because the motion of the source of the waves affects the relative motion between the source and the observer. When the source moves towards the observer, the waves emitted by the source become compressed, resulting in a shorter wavelength. Conversely, when the source moves away from the observer, the waves become stretched, leading to a longer wavelength.
In the case of a blinking light source moving towards an observer, each blink of light emitted by the source will have a shorter wavelength compared to the emitted wavelength when the source is at rest relative to the observer. This change in wavelength is referred to as blue shift because there is a shift towards shorter wavelengths, which correspond to higher frequencies and higher energy.
The amount of wavelength shift depends on the relative velocity between the source and the observer and is described by the Doppler effect equation. If the relative velocity is significant compared to the speed of light, the effect becomes more pronounced.
It's important to note that the Doppler effect is not limited to light waves but is applicable to all types of waves, including sound waves. The same principle applies to sound waves, where the motion of the source affects the observed frequency and perceived pitch of the sound.