Tag: image formation by lens

Questions Related to image formation by lens

The diameter of the sun is $1.4 \times 10 ^ { 9 } \mathrm { m }$ and its distance from the earth is $1.5 \times 10 ^ { 11 } \mathrm { m } .$ The radius of the image of the sun formed by a lens of focal length $20 \mathrm { cm }$ is

image formation by lens image formation by lenses ray optics and optical instruments optics physics

  1. $93 mm$

  2. $0.093mm$

  3. $9.3 mm$

  4. $0.93 mm$

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Correct Option: D

An object of length 2.0 cm is placed perpendicular to the principal axis of a convex lens of focal length 12 cm. Find the size of the image if the object is at a distance of 8.0 cm from the lens.

image formation by lens image formation by lenses ray optics and optical instruments optics physics

  1. $6 cm$

  2. $4 cm$

  3. $5 cm$

  4. $1 cm$

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Correct Option: A

A man wearing glasses of focal length  $+ 1 \mathrm { m }$  cannot clearly see beyond  $1\mathrm { m }$

image formation by lens image formation by lenses ray optics and optical instruments optics physics

  1. if he is farsighted

  2. if he is nearsighted

  3. if his vision is normal

  4. in each of these case

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Correct Option: D
Explanation:
That is the person is near-sighted.
And the condition is known as myopia.
Ans. (b)

A thin lens produces an image of the same size as the object. Then from the optical centre of the lens, the distance of the object is

image formation by lens image formation by lenses ray optics and optical instruments optics physics

  1. zero

  2. $4f$

  3. $2f$

  4. $f/2$

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Correct Option: C

Optical axis of a thin equi-convex lens  is the X-axis. The co-ordinate of a point object and its image are (-20 cm, 1 cm) and (25 cm, -2 cm) respectively:-

image formation by lens image formation by lenses ray optics and optical instruments optics physics

  1. The lens is located at X = 5 cm

  2. The lens is located at X = -5 cm

  3. The focal length of the lens is 10 cm

  4. The focal length of the lens is 15 cm

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Correct Option: B,C

A point object $O$ is placed on the principle axis of a convex lens of focal length $20\ cm$ at a distance of $40\ cm$ to the left of it. The diameter of the lens is $10\ cm$. If the eye is placed $60\ cm$ to the right of the lens at a distance $h$ below the principle axis, then the maximum value of $h$ to see the image will be

image formation by lens image formation by lenses ray optics and optical instruments optics physics

  1. $2.5\ cm$

  2. $5\ cm$

  3. $0\ cm$

  4. $10\ cm$

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Correct Option: A

For two position of lens, the images are obtained on a fixed screen. If the size of the object is 2 cm and size of diminished image is 0.5 cm, the size of the other image will be

image formation by lens image formation by lenses ray optics and optical instruments optics physics

  1. 1 cm

  2. 4 cm

  3. 8 cm

  4. 16 cm

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Correct Option: C
Explanation:

$height^{2} _{object}=height _{image1}\times height _{image2}$


$2 \times 2=0.5 \times h$

$h=8$

option $C$ is correct

A lens is placed between the source of light and a wall. It forms images of area $ { A } _{ 1 }$ and  ${ A } _{ 2 }$ on the wall for its two different positions. The area of the source of light is :

image formation by lens image formation by lenses ray optics and optical instruments optics physics

  1. $ \sqrt { { A } _{ 1 }{ A } _{ 2 } } $

  2. $ \dfrac { { A } _{ 1 }+{ A } _{ 2 } }{ 2 } $

  3. $ { \left( \dfrac { \sqrt { { A } _{ 1 } } +\sqrt { { A } _{ 2 } } }{ 2 } \right) }^{ 2 } $

  4. $None\ of\ these$

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Correct Option: A
Explanation:

$height^{2} _{object}=height _{image1} \times height _{image2}$


$r^{2} _{source}=r _{image1} \times r _{image2}$

$\pi r^{2} _{source}=\pi r _{image1} \times r _{image2}$

$A _{source}=\sqrt{\pi^{2} r^{2} _{image1}r^{2} _{image2}}$

$A _{source}=\sqrt{A _{1}A _{2}}$

option $A$ is correct 

A student focused the image of a candle flame on a white screen using a convex lens. He noted down the position of the candle, screen and the lens as under position of candle $=12.0\ cm$position of convex lens $=50.0\ cm$position of the screen $=88.0\ cm$. Where will the image be formed, if he shifts the candle towards the lens at a position of $31.0\ cm$?

image formation by lens image formation by lenses ray optics and optical instruments optics physics

  1. 19cm

  2. 48cm

  3. Infinity

  4. at center of curvature

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Correct Option: C

A magnifying glass is to be used at the fixed object distance of $1$ inch. If it is to produce an erect image $5$ items magnified, its focal length should be- 

image formation by lens image formation by lenses ray optics and optical instruments optics physics

  1. $0.2"$

  2. $0.8"$

  3. $1.25"$

  4. $5"$

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Correct Option: B