The time taken by light to travel from Sun to Earth is approximately:
A. 8 minutes
B. 1 hour
C. 8 seconds
D. 1 day
Answer: Option A
Solution (By JKSSB Mock Tests)
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:
Iris adjusts pupil size. In bright light pupil constricts, dim light dilates. Retina forms image. Cornea and lens focus. Eye is like camera.
Explanation:
Joule's Law of Heating states that the heat (H) produced in a resistor is given by H = I²Rt. This indicates that the heat produced is directly proportional to the square of the electric current (I), directly proportional to the resistance (R), and directly proportional to the time (t) the current flows.
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