Speed of light
Speed of light is a Science & Technology concept from the MPSC syllabus, tested in 4 past MPSC questions (2017, 2021). Below are those real questions with their correct answers and explanations, plus the concepts worth being comfortable with first.
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लांबीचे नवीन एकक असे निवडले की ज्यानुसार निर्वात पोकळीत प्रकाशाची गती 1 एकक येते. जर सूर्यप्रकाश, सूर्यापासून पृथ्वीपर्यंतचे अंतर 8 मिनिट व 20 सेकंदात कापत असेल, तर लांबीच्या नवीन एककानुसार सूर्य व पृथ्वीमधील अंतर किती ? A new unit of length is chosen such that the speed of light in vacuum is unity. What is the distance between the Sun and the Earth in terms of the new unit, if light takes 8 minutes and 20 seconds to cover this distance ?
Time = 8 min 20 sec = 500 seconds. Since speed of light is 1 unit in the new system, distance = speed × time = 1 × 500 = 500 units.
प्रकाशाचा वेग ____________ असतो. Speed of light is ____________.
The speed of light in a vacuum is a fundamental physical constant, approximately equal to 3 × 10⁸ meters per second.
जर प्रकाश पहिल्या माध्यमातून 2 × 10⁸ ms⁻¹ वेगाने जाताना दुसऱ्या माध्यमात त्याचा वेग 1.25 × 10⁸ ms⁻¹ होत असेल तर दुसऱ्या माध्यमाचा पहिल्या माध्यमाच्या संदर्भातील अपवर्तनांक काढा. Find the refractive index of the second medium with respect to the first medium, if light moves through the first medium with velocity 2 × 10⁸ ms⁻¹, which changes to 1.25 × 10⁸ ms⁻¹ in the second medium.
Refractive index of second medium with respect to first medium is given by the ratio of speed of light in the first medium to that in the second medium: (2 × 10⁸) / (1.25 × 10⁸) = 1.6.
लेसर किरण पृथ्वीवरून चंद्रकड सोडूननंतर चंद्राच्या पृष्ठभागापासून परावर्तित होऊन पृथ्वीवर परत येण्यास 2.56 सेकंद लागतात. तर चंद्राच्या पृथ्वीभोवतीच्या परिभ्रमण कक्षेची त्रिज्या किती ? A laser light beamed at the Moon takes 2.56 s to return to earth after reflection at the Moon's surface. How much is the radius of the lunar orbit around the Earth ?
Time taken for round trip is 2.56 s, so time to reach the moon (t) = 2.56 / 2 = 1.28 s. Distance (Radius) = Speed of light * time = (3 × 10⁸) × 1.28 = 3.84 × 10⁸ m.