Solve Study Textbooks Guides

Use app

Login

>>Class 12
>>Physics
>>Ray Optics and Optical Instruments
>>Combination of Lenses
>> $A plano - convex lens is made of a mater$

Question

A plano-convex lens is made of a material of refractive index $n$ . When a small object is placed $30$ cm away in front of the curved surface of the lens, an image of double the size of the object is produced. Due to reflection from the convex surface of the lens, another faint image is observed at a distance of $10$ cm away from the lens. Which of the following statement (s) is (are) true?

This question has multiple correct options

A

The refractive index of the lens is $2.5$

B

The radius of curvature of the convex surface is $45$ cm

C

The faint image is erect and real

D

The focal length of the lens is $20$ cm

Hard

Open in App

Updated on : 2022-09-05

Solution

Verified by Toppr

Correct options are A) and D)

Case I,

$\frac{1}{6 0} + \frac{1}{3 0} = \frac{1}{f _{1}}$

$f_{1} = 20 c m$

Case II,

$\frac{1}{1 0} - \frac{1}{3 0} = \frac{1}{f _{2}}$

$f_{2} = 15 = \frac{R}{2}$

$R = 30 c m$

From case I,

$f_{1} = \frac{R}{n - 1} = 20$

Thus, $n = 2.5$

Radius of curvature is $30 c m$

Focal length of lens is $f_{1} = 20 c m$

Answer is option A and D.

Video Explanation

Solve any question of Ray Optics and Optical Instrument with:-

Patterns of problems

Was this answer helpful?

0

0

Similar questions

A plano convex lens of refractive index 1.5 and radius of curvature 30 cm is silvered at the curved surface. Now this lens has been used to from the image of an object. At what distance from this lens an object be placed in order to have a real image of the size of the object :

A piano-convex lens of refractive index 1.5 and radius of curvature 30 cm is silvered at the curved surface. Now this lens has been used to form the image of an object. At what distance from this lens an object be placed in order to have a real image of the size of the object ?

An object is placed 20 cm in front of a plano convex lens of focal length 15 cm. The plane surface of the lens is silvered. The image will be formed at a distance

153552

A plano-convex lens is made of a material of refractive index u = 1.5. The radius of curvature of curved surface of the lens is 20 cm. If its plane surface is silvered, the focal length of the slivered lens will be

A plano-convex of refractive index 1.5 and radius of curvature 30 cm is silvered at the curved surface. Now this lens has been used to form the image of an object. At what distance from this lens, an object be placed in order to have a real image of the size of the object?

More From Chapter

Ray Optics and Optical Instruments

View chapter >

Revise with Concepts

Combination of Lenses in Contact

ExampleDefinitionsFormulaes

Problems on Lenses

ExampleDefinitionsFormulaes

Learn with Videos

Power of a Lens

Effective Focal Length

Numericals on Combination of Lenses

Complex Numericals based on Thin Lenses

Practice more questions

Medium Questions

Shortcuts & Tips

Problem solving tips

Common Misconceptions

Memorization tricks

Important Diagrams