No, the wavelength of light does not change when it passes through a double-slit experiment. The wavelength of light is an inherent property of the electromagnetic wave itself and remains constant unless the light interacts with a medium that can cause a change in its wavelength, such as refraction or dispersion.
In a double-slit experiment, a beam of light is passed through two narrow slits, creating two sources of light that act as secondary wavefronts. These secondary wavefronts then interfere with each other, producing an interference pattern on a screen placed behind the slits.
The interference pattern arises from the interaction of the original light wave with itself, causing constructive and destructive interference. The spacing of the interference fringes (bright and dark bands) on the screen is determined by the wavelength of the light used in the experiment. The interference pattern is a result of the interaction between the original light wave and the two secondary wavefronts, and it does not cause a change in the light's wavelength.
Regarding your statement about the number of detectable wavelengths, it is true that there is a wide range of wavelengths within the electromagnetic spectrum. The electromagnetic spectrum encompasses various forms of electromagnetic radiation, including visible light, radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays. Each of these regions within the spectrum corresponds to a specific range of wavelengths.
Visible light, which is the portion of the electromagnetic spectrum that our eyes can perceive, spans a specific range of wavelengths approximately between 400 and 700 nanometers (nm). Within this range, different colors are associated with specific wavelengths. However, there are indeed many more wavelengths of electromagnetic radiation beyond the visible spectrum, such as radio waves with much longer wavelengths and gamma rays with much shorter wavelengths.
So, while there are billions of detectable wavelengths within the entire electromagnetic spectrum, the specific wavelength of light used in a double-slit experiment remains constant throughout the experiment.