The resolving power of an astronomical telescope can be significantly increased by:
A. Increasing the focal length of the objective lens.
B. Increasing the aperture (diameter) of the objective lens.
C. Using light of a longer wavelength.
D. Decreasing the focal length of the eyepiece.
Answer: Option B
Solution (By JKSSB Mock Tests)
Resolving power is a telescope's ability to distinguish closely spaced objects (like double stars) as separate. It is proportional to D / lambda, where D is the diameter (aperture) of the objective lens and lambda is the wavelength of light. Increasing the aperture D directly and strictly increases the resolving power.
Explanation:
Average Earth-Sun distance (1 AU) ≈ 1.5×10¹¹ m. Speed of light c = 3×10⁸ m/s. Time t = distance/speed = 1.5×10¹¹ / 3×10⁸ = 500 seconds ≈ 8.33 minutes ≈ 8 minutes. This is a standard astronomical fact. Memory aid: 'Sunlight takes 8 minutes to reach Earth; we see the Sun as it was 8 minutes ago'. This factual knowledge question tests awareness of scale in physics, frequently appearing in competitive exams. Always recall key constants: Earth-Sun distance, light speed, for quick estimations.
Explanation:
Newton's third law states: for every action, there is an equal and opposite reaction. These forces act on two different interacting bodies, hence they never cancel each other as they don't act on the same body. They can act at a distance (e.g., gravitational forces) or through contact. Cancellation of forces occurs only when multiple forces act on a single body. This distinction is crucial for free-body diagram analysis. Exam tip: Always identify which body each force acts upon. Misconception about force cancellation is a common trap in competitive exam questions testing Newton's laws.
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