Answer: c. refracting telescopes
Step-by-step explanation:
Refracting telescopes have an optical system consisting of a set of lenses that have the property of deflecting (refracting) the light that passes through them.
In this way, the images captured from distant objects converge on a point in the focal plane of the telescope.
However, the main disadvantage of this type of telescope is the chromatic aberration, which produces annoying color halos (mainly red and blue) around the image.
It should be noted that the chromatic aberration occurs because the different wavelengths that make up the light (the colors of the light) that passes through the objective lens deviate (refract) in different ways, causing them not to focus on the same point. For example, blue wavelengths are focused before the green wavelengths and these before the red ones. And this problem is stronger the shorter the focal length of the lens is.