Indian Navy AA (Artificer Apprentice) The Human Eye and the Colourful World — practice questions

Explore 2 free The Human Eye and the Colourful World questions in Indian Navy AA (Artificer Apprentice) Physics. Open each question or exercise to read its content, reference answers and available explanation.

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The Human Eye and the Colourful World questions and exercises with answers

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A myopic person uses a lens of focal length -1.5 m. The power of this lens is:Read the answer and worked solution →Why do planets NOT twinkle though stars do?Read the answer and worked solution →

Worked practice questions

A myopic person uses a lens of focal length -1.5 m. The power of this lens is:

-0.67 D
+0.67 D
+1.5 D
-1.5 D

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Correct answer: A. -0.67 D

1. Power of a lens P = 1 / f (with f in metres). 2. Given f = -1.5 m. 3. Substitute: P = 1 / (-1.5) = -0.6666... D. 4. Rounded to two decimals, P approx -0.67 D. 5. The minus sign confirms a diverging (concave) lens, as expected for myopia. _Source: syllabus Science Ch 11 'Human Eye and the Colourful World'_

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Why do planets NOT twinkle though stars do?

Planets are too dim in the standard view
Planets do not emit light
Planets are bigger than the wave-front fluctuations
Planets are inside our atmosphere

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Correct answer: C. Planets are bigger than the wave-front fluctuations

1. Stars are essentially point sources because of their huge distance. 2. Atmospheric refraction shifts the tiny image of a star at random. 3. Planets are closer and appear as extended discs. 4. Random shifts across an extended disc average out. 5. So a planet's overall brightness stays steady, while a star flickers. 6. Hence planets do not twinkle. _Source: syllabus Science Ch 11 'Human Eye and the Colourful World'_