Read the excerpt from Chapter Three of Windows to the Universe: Revolutions in Astronomy.Refracting telescopes, which use lenses to gather and focus light, need lenses made from pure, bubble-free glass. These lenses must be ground and polished with great precision. Reflecting telescopes require mirrors shaped into precise parabolic curves. Any mistake in shaping or polishing the lenses or mirrors could result in blurry images.How does the author create an informative tone in this excerpt?