alleryStart learning →A spherical mirror has a radius of curvature of 24 cm. Its focal length is:
- 6 cm
- 48 cm
- 24 cm
- 12 cm
Show answer and solution
Correct answer: D. 12 cm
We have f = R/2.
That is f = 24/2.
So f = 12 cm.
Indian Navy Pilot Light - Reflection and Refraction — practice questions
Explore 2 free Light - Reflection and Refraction questions in Indian Navy Pilot Science. Open each question or exercise to read its content, reference answers and available explanation.
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Worked practice questions
A convex lens of focal length 20 cm produces a real image at distance 60 cm. The object is at:
- 60 cm in front of the lens
- 20 cm in front of the lens
- 30 cm in front of the lens
- 15 cm in front of the lens
Show answer and solution
Correct answer: C. 30 cm in front of the lens
1. Use lens formula 1/v - 1/u = 1/f (note sign convention for lenses).
2. v = +60 cm, f = +20 cm. So 1/u = 1/v - 1/f = 1/60 - 1/20 = (1-3)/60 = -2/60.
3. u = -30 cm, i.e. 30 cm in front of the lens.
_Source: syllabus Science, Ch 9 "Light Reflection and Refraction", §9.4.4_
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