Test: Refraction by Lens - NEET MCQ

# Test: Refraction by Lens - NEET MCQ

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## 10 Questions MCQ Test Physics Class 12 - Test: Refraction by Lens

Test: Refraction by Lens for NEET 2024 is part of Physics Class 12 preparation. The Test: Refraction by Lens questions and answers have been prepared according to the NEET exam syllabus.The Test: Refraction by Lens MCQs are made for NEET 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Refraction by Lens below.
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Test: Refraction by Lens - Question 1

### We wish to make a plano convex lens of focal length 16 cm from glass having refractive index 1.5. It is to be used in air. What should be the radius of curvature of the curved surface?​

Detailed Solution for Test: Refraction by Lens - Question 1

Test: Refraction by Lens - Question 2

### A convergent lens made of crown glass (refractive index 1.5) has focal length 20cm in air. If it is immersed in a liquid of refractive index 1.60, its focal length will be:​

Detailed Solution for Test: Refraction by Lens - Question 2

When the lens is in air, we have (from lens maker's equation), 1/20 = [(1.5/1) - 1) (1/R1- 1/R2).
We are not bothered about the signs of R1 and R2 since they are unknown quantities.
Even though we know that the convergent lens will become divergent in the denser medium, we write the lens maker's equation without bothering about the sign of its unknown focal length in the liquid. If if is the focal length in the liquid, we can write,
1/f = ((1.5/1.6) - 1) (1/R1 - 1/R2).
Dividing the first equation by the second, we obtain f/20 = 0.5x1.6/(-0.1) from which f = -160 cm

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Test: Refraction by Lens - Question 3

### If R1 and R2 are the radii of curvature of a double convex lens, which of the following will have the largest power?​

Detailed Solution for Test: Refraction by Lens - Question 3

Using the lens maker’s formula we get
p= (μ−1) (1/R1​+1/R2​)
As we can clearly see, when R1= R2= 5cm then the maximum power is achieved.

Test: Refraction by Lens - Question 4

A concave lens of glass, refractive index 1.5, has both surfaces of same radius of curvature R. On immersion in a medium of refractive index 1.75, it will behave as a:​

Detailed Solution for Test: Refraction by Lens - Question 4

Consider refraction of light from infinity at first surface,
(μ2/v)​​−( μ1/u​)​=(μ2​−μ1/R)​​
(1.5​/ v1​)-(1.75/−∞)​=1.5−1.75​/−R
Consider refraction of this image from second surface,
​(1.75​/ v2)−(​1.5/v1)​=(1.75−1.5​)/R
Hence, v2​=3.5R
This is the image of light coming from infinity, therefore the focal length.
It is converging since focal length is positive.

Test: Refraction by Lens - Question 5

If two thin lenses of focal length f1 and f2 are held in contact then the focal length of the combination will be

Test: Refraction by Lens - Question 6

A convex lens produces a real image m times the size of the object. What is the distance of the object from the lens?

Detailed Solution for Test: Refraction by Lens - Question 6

M=−ϑ /u ​=−m/1​
ϑ=−mu
(1/ϑ​)−(1/u)​=1/f
1/mu​+1/u​=−1/f​
(1+m)​/xu=−1/f​
u= (1+m)​f/(m)

Test: Refraction by Lens - Question 7

What is the unit of power of lens?

Test: Refraction by Lens - Question 8

A double convex thin lens made of glass of refractive index 1.6 has radii of curvature 15 cm each. The focal length of this lens when immersed in a fluid of refractive index 1.63 is​

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Test: Refraction by Lens - Question 9

1 dioptre =​

Detailed Solution for Test: Refraction by Lens - Question 9

A dioptre (British spelling) or dioptre (American spelling) is a unit of measurement of the optical power of a lens or curved mirror, which is equal to the reciprocal of the focal length measured in metres. (1 dioptre = 1 m−1.) It is thus a unit of reciprocal length.

Test: Refraction by Lens - Question 10

If two thin lenses of power p1 and p2 are held in contact then the power of the combination will be​

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## Physics Class 12

105 videos|425 docs|114 tests