Final answer:
The focal length of a telescope's objective lens is indeed much larger than that of the eyepiece, which contributes to a higher angular magnification, making the assertion and reason true, with the reason correctly explaining the assertion (Answer A).
Step-by-step explanation:
The assertion and reason stated in the question pertain to the optical principles of telescopes. The assertion mentions that the focal length of the objective lens in a telescope is much more than that of the eyepiece. This is true because the long focal length of the objective lens ensures a wider distance over which light can be collected and brought to focus, resulting in a smaller, detailed intermediate image of distant objects.
The reason provided is that the telescope has high resolving power due to the large focal length. This statement is true, but a clarifying point is necessary: the high resolving power is also related to the diameter of the objective lens and the quality of the optics, not just the focal length. However, a longer focal length of the objective does contribute to the higher angular magnification of the telescope because angular magnification is the ratio of the focal length of the objective to the focal length of the eyepiece (M = fo/fe).
Therefore, the correct answer is A: Both assertion and reason are true, and the reason is the correct explanation of the assertion.