3 of 12 Telescopes used for research do not use eyepieces. Why not? Eyepieces are not needed once the primary mirror lens becomes sufficiently large. Eyepieces are too far above the ground to reach with large telescopes. CCD detectors (sensors) are superior to the human eye for collecting photons. Large telescopes do not have sufficiently high resolving power to benefit from using an eyepiece 4 of 12 How much of a radioactive element remains after a time of 3 half-lives? 1/16 1/8 1/4 1/2 None of the above, because it depends on the specific element.

Telescopes that are used for research purposes do not always use eyepieces. CCD detectors (sensors) are better at collecting photons than the human eye. CCD sensors are therefore used in place of the eyepiece in some telescopes. Therefore option (A) is correct answer and 18 radioactive element.

Since CCD sensors detect light more accurately and precisely than the human eye, they are frequently used instead of eyepieces. The correct answer is: CCD detectors (sensors) are superior to the human eye for collecting photons.

The amount of radioactive material that remains after a certain period of time can be calculated using the formula:

Amount = initial amount × (1/2) /(number of half-lives)

The amount of a radioactive element that remains after 3 half-lives can be calculated by substituting 3 for the number of half-lives. So, the answer to the question is:

1/8 (which is 1/2 × 1/2 × 1/2 = 1/8)

Therefore, the answer is: 1/8.

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