Which of the following is an example of a third class lever? MCQ with Answer and Explanation
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Question #1
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An electric heater of resistance 10 Ω draws current 5 A. Power consumed is
Question #2
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One Parsec is a unit of astronomical distance. It is defined as the distance at which a radius of one astronomical unit (AU) subtends an angle of one second of arc. One parsec is approximately equal to:
Correct Answer: Option D
Explanation:
The parsec (parallax second) is the largest standard unit of distance used in astronomy. 1 Astronomical Unit (AU) is approx 1.5 x 10^11 m. 1 Light Year (ly) is approx 9.46 x 10^15 m. 1 Parsec is approximately 3.08 x 10^16 m. Converting parsecs to light years: (3.08 x 10^16) / (9.46 x 10^15) ≈ 3.26 light years.
The parsec (parallax second) is the largest standard unit of distance used in astronomy. 1 Astronomical Unit (AU) is approx 1.5 x 10^11 m. 1 Light Year (ly) is approx 9.46 x 10^15 m. 1 Parsec is approximately 3.08 x 10^16 m. Converting parsecs to light years: (3.08 x 10^16) / (9.46 x 10^15) ≈ 3.26 light years.
Question #3
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The phenomenon of total internal reflection occurs when light travels from:
Correct Answer: Option C
Explanation:
Total internal reflection (TIR) requires: (1) light travels from denser to rarer medium (n₁ > n₂), and (2) angle of incidence exceeds critical angle θ_c = sin⁻¹(n₂/n₁). Option A describes refraction toward normal; B describes partial reflection/refraction; D is incorrect. Memory aid: 'TIR: denser→rarer AND i > θ_c'. This condition-based question tests optics fundamentals, frequently examined in competitive exams. Always verify both conditions for TIR; common applications include optical fibers and prisms in binoculars.
Total internal reflection (TIR) requires: (1) light travels from denser to rarer medium (n₁ > n₂), and (2) angle of incidence exceeds critical angle θ_c = sin⁻¹(n₂/n₁). Option A describes refraction toward normal; B describes partial reflection/refraction; D is incorrect. Memory aid: 'TIR: denser→rarer AND i > θ_c'. This condition-based question tests optics fundamentals, frequently examined in competitive exams. Always verify both conditions for TIR; common applications include optical fibers and prisms in binoculars.
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