Chapter 5, Problem 1QFR

What is light-gathering power? How does it affect the ability to see faint objects?

To determine

The light-gathering power, and to check its effect on the ability to see faint objects.

Answer to Problem 1QFR

Light-gathering power is the capability of a telescope to accumulate a large amount of photons than the human eye. The greater the area of collecting of the telescope the brighter the object.

Explanation of Solution

When photons from any object strike a person’s retina he or she will be capable to see the object if the quantity of photons are large enough to trigger chemical reactions in nerve cells. The brightness of the object is dependent on the number of photons that enter his or her eye per second, and the number differs according to the size of each person’s eyes pupils.

Light-gathering power rely on the collecting area of the mirror. In case of telescopes the greater its collecting area the more the photons it collects. Thus, a telescope with a larger diameter lens will have greater light-gathering power. Since a larger telescope can produce a brighter image, this allows a person to see faint stars that are invisible in telescopes with smaller gathering area.

Therefor light-gathering power is the capability of a telescope to collect a large amount of photons than the human eye. Also greater the area of collecting the brighter the object.