SATHEE: Ray Optics and Optical Instruments

Ray Optics and Optical Instruments - Result Question 49

51. Focal length of a convex lens of refractive index 1.5 is $2 c m$ . Focal length of the lens when immersed in a liquid of refractive index of 1.25 will be

[1988]

(a) $10 c m$

(b) $2.5 c m$

(d) $7.5 c m$

Topic 4: Prism & Dispersion of Light

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Answer:

Correct Answer: 51. (c)

Solution:

(c) $\frac{f_{a}}{f_{l}} = \frac{(\frac{μ_{g}}{μ_{l}} - 1)}{(μ_{g} - 1)} = \frac{(\frac{1.5}{1.25} - 1)}{1.5 - 1} = \frac{\frac{1}{5}}{\frac{1}{2}} = \frac{2}{5}$

$f_{l} = \frac{5}{2} f_{a} = \frac{5}{2} \times 2 = 5 c m$

Ray Optics and Optical Instruments - Result Question 49

51. Focal length of a convex lens of refractive index 1.5 is $2 c m$ . Focal length of the lens when immersed in a liquid of refractive index of 1.25 will be

Answer:

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Ray Optics and Optical Instruments - Result Question 49

51. Focal length of a convex lens of refractive index 1.5 is 2cm. Focal length of the lens when immersed in a liquid of refractive index of 1.25 will be

Answer:

Engineering Preparation

Medical Preparation

NCERT Books & Solutions

Important Resources

Other Resources

Syllabus

Test Platform

Sample Mock Test

Mentorship

NCERT Exercise Video Solution

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51. Focal length of a convex lens of refractive index 1.5 is $2 c m$ . Focal length of the lens when immersed in a liquid of refractive index of 1.25 will be