Reference Material:
The aperture of a telescope is several times larger than the aperture of the human eye so that the objects can not be normally seen by unaided eye can be seen. Light gathering power of a telescope is proportional to the area of its aperture and hence depends on the square of the radius of the mirror. Therefore, a 20 cm diameter telescope collects four times more photons than a 10 cm diameter telescope.
A telescope can be equipped to record light over a long period of time, by using photographic film or electronic detectors such as photometers or CCD detectors while the eye has no capability to store light. Along-exposure photograph taken through a telescope reveals objects too faint to be seen with the eye, even by looking through the same telescope.
A third major advantage of large telescopes is that they have superior resolution, the ability to discern fine detail. Small resolution is good. The resolution is directly proportional to the wavelength being observed and inversely proportional to the diameter of the telescope.
Sample Answer:
We can use telescopes by eye. Since telescopes improve details with enough light, we make the telescope larger to collect lights. We can see more features and details. Fractions can make images blurry. We make the 10 times telescope to see the details 10 times bigger than they are. Modern digital telescope is widely used in astronomy, which is 100 times more effective than our own eyes. (67 words)
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