Tag: human eye and colourful world

Questions Related to human eye and colourful world

A far sighted person can see object beyond $71\;cm$ clearly if the separation between the glasses and eye lens is $2\;cm$, then find the focal length of glasses.

structure of human eye human eye and colourful world

  1. $23\;cm$

  2. $34.5\;cm$

  3. $18.4\;cm$

  4. $30\;cm$

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Correct Option: C

A person suffering from eyesight defect has far point at $40cm$ and near point at $25cm$. The person uses a lens to see far away object. Find the near point of the person while wearing this lens.

structure of human eye human eye and colourful world

  1. $50cm$

  2. $\dfrac{200}{13}cm$

  3. $\dfrac{200}{3}cm$

  4. $25cm$

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Correct Option: C

A farsighted woman breaks her current eyeglasses and is using an old pair whose refractive power is 1.660 diopters. Since these eyeglasses do not completely correct her vision, she must hold a newspaper 42.00 cm from her eyes in order to read it. She wears the eyeglasses 2.00 cm from her eyes. How far is her near point from her eyes?

structure of human eye human eye and colourful world

  1. 75 cm

  2. 125 cm

  3. 225 cm

  4. 121.05 cm

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Correct Option: D
Explanation:
The refractive power of the lens is $1.660$ dipters. So the focal length of the lens is $f=\dfrac{1}{1.660}=0.6024\,m=60.24\,cm$

The distance between the newpaper and her eyes is $42.00\,cm$

The distance between her eyes and glasses is $2.00\,cm$

So, the distance between the lglasses and newspaper is $(42.00-2.00)\,cm=40.00\,cm.$ That is, $d _0=40.00\,cm$

The distance $(d _i)$ between the glasses and the virtual image formed by the lens given by,

$d _i=\dfrac{fd _0}{d _0-f}=\dfrac{60.24-40.00}{40.00-60.24}=-119.05\,cm$

This relation is obtained from thin lens equation and the negative sign implies the image is virtual.

This position is her near point.

So the near point from her eyes is, $119.05\,cm+2.00\,cm=121.05\,cm$

Myopia can be corrected by using spectacle having ________.

structure of human eye human eye and colourful world

  1. Concave lens

  2. Convex lens

  3. Biconvex lens

  4. Biconcave lens

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Correct Option: A

A girl whose eyes are $150  \mathrm{cm}  $ above the ground looks at her reflection in a vertical mirror $ 250  \mathrm{cm}  $ away. The top and bottom of the mirror are $200 \mathrm{cm}  $ and  $120 \mathrm{cm} $ above the ground respectively. What length below her eyes can she see of herself in the mirror?

structure of human eye human eye and colourful world

  1. $60 cm$

  2. $75 cm$

  3. $100 cm$

  4. $120 cm$

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Correct Option: D

A student of class $  10,  $ is not able to see clearly the black board question when seated at a distance of $5  \mathrm{m}  $ from the board,the defect he is suffering from is

structure of human eye human eye and colourful world

  1. Myopia

  2. Hypermetropia

  3. Presbyopia

  4. Astigmatism

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Correct Option: A

A man can see clearly up to $3\ \textit{metres}$. Prescribe a lens for his spectacles so that he can see clearly up to $12\ \textit{metres}$

structure of human eye human eye and colourful world

  1. $-3/4\ D$

  2. $3\ D$

  3. $-1/4\ D$

  4. $-4\ D$

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Correct Option: C

Myopia is a defect of vision caused by

structure of human eye human eye and colourful world

  1. decrease in the retinal distance from the lens

  2. a decrease in the diameter of the eyeball

  3. an increase in the thickness of the lens

  4. an increase in the curvature of the lens

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Correct Option: D

A professor reads a greeting card on his 50th birthday with +2.5D glasses keeping the card 25 cm away. 10 years later he reads the greeting card  with same glasses keeping the card 50 cm away.What power should he wear now?

structure of human eye human eye and colourful world

  1. 2D

  2. 0.5D

  3. 2.25D

  4. 4.5D

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Correct Option: D
Explanation:

$ \dfrac { 1 }{ { f }^{ ' } } =\dfrac { 1 }{ 25 } -\dfrac { 1 }{ 50 } =\dfrac { 1 }{ 50 } \quad or$


$ P=2D$

${ p } _{ net }=2.5+2=4.5D$

A person cannot see distinctly at the distance less than one metre. Calculate the power of the lens that he should use to read a book at a distance of $25\, cm$

structure of human eye human eye and colourful world

  1. $+ 3.0\, D$

  2. $+ 0.125\, D$

  3. $- 3.0\, D$

  4. $+ 4.0\, D$

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Correct Option: A