Tag: human eye and colourful world

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Questions Related to human eye and colourful world

Multiple choice physics human eye and colourful world sunlight - white and coloured sunlight - combination of 7 lights fibre optics basics

What does the dispersion of light in a medium imply
i) Lights of different wavelength travel with different speeds in the medium.
ii) Light of any frequency will travel with the same speed in the medium
iii) The refractive index of the medium is different for different wavelength of light

  1. $(i)$ and $(ii)$ only
  2. $(ii)$ and $(iii)$ only
  3. $(i)$ and $(iii)$ only
  4. $(i),(ii)$ and $(iii)$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Dispersion occurs because the refractive index of a medium depends on the wavelength of light. Since refractive index is related to the speed of light in the medium (n = c/v), different wavelengths travel at different speeds, causing them to deviate by different amounts.

Multiple choice structure of human eye human eye and colourful world

A person cannot see object clearly that are closed that $2m$ and father than $4m$ . To correct the eye vision the person will use :

  1. Bifocal lenses of power $0.5D$ and $0.25D$
  2. Bifocal lenses of power $0.25 D$ and $3.5D$
  3. Bifocal lenses of power $0.5 D$ and $4.0 D$
  4. Bifocal lenses of power $4.0 D$ and $0.5 D$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given,

The distance of the far point $(D) = 2m$
Let f be the focal length of the eye lens.
Image distance ( distance between eye lens and retina ) for our human eye is always constant and is about 
 $0.25m.$
This is due to the action of ciliary muscles. 
applying lens formula, we get 
$f = -D = -2 m.$
But, the power of a lens is reciprocal of focal length.
Hence. Power $=\dfrac{1}{f}.$ ( f in meters )
$\dfrac{1}{-2}=0.5$D
Similarly,
The distance of the far point $(D) = 4m$
Let f be the focal length of the eye lens.
Image distance ( distance between eye lens and retina ) for our human eye is always constant and is about 
 $0.25m.$
This is due to the action of ciliary muscles.
applying lens formula, we get 
$f = -D = -4 m.$
But, the power of a lens is reciprocal of focal length.
Hence. Power $=\dfrac{1}{f}.$ ( f in meters )
$\dfrac{1}{-4}=0.25$D
So he has to use by focal lenses

Multiple choice structure of human eye human eye and colourful world

To remove myopia (short sightedness) a lens of power $- 0.66D$ is required. The distant point of the eye is approximately

  1. $100$ cm
  2. $151.5$ cm
  3. $50$ cm
  4. $25$ cm
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The far point of a nearsighted eye is equal to the focal length of the correcting lens in magnitude. Using f = 1 / P, with P = -0.66 D, f = 1 / -0.666... = -1.5 m = -150 cm, approximately 151.5 cm.

Multiple choice structure of human eye human eye and colourful world

Minimum and maximum distance should be for clear vision of healthy eye.

  1. 100 cm & 500 cm

  2. Infinite & 25 cm

  3. 25 cm & 100 cm

  4. 25 cm & infinite
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Minimum distance for clear vision of healthy eye is  $25 \ cm$ and maximum distance is infinite.

Multiple choice structure of human eye human eye and colourful world

Diameter of a human eye lens is 2 millimetre. What will be the minimum distance between two points to resolve, which are situated at the distance of 50 m from the eye? The wavelength of light is 5000 angstrom.

  1. 2.32 m

  2. 4.28 mm

  3. 1.25 cm

  4. 12.48 cm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Using the diffraction limit of resolution, the minimum resolvable distance d is given by d = 1.22 * lambda * L / D, where lambda is wavelength, L is distance to the object, and D is the lens diameter. Substituting lambda = 5 * 10^-7 m, L = 50 m, and D = 2 * 10^-3 m yields d = 1.25 cm.

Multiple choice structure of human eye human eye and colourful world

State whether true or false:

A concave lens is used to correct short-sightedness in eye.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer is A.

A person who is short sighted can focus clearly on near objects but cannot focus on distant objects. This is because the eyeball is too long. Light from distant objects is focused at a point in front of the retina resulting in a blurred image.
This defect can be corrected by wearing a concave (diverging) spectacle lens. The rays of light from a near object are diverged before entering the eye so that the cornea and eye lens can direct the focal point onto the retina.
Hence, the statement is true.

Multiple choice structure of human eye human eye and colourful world

A person cannot see the object beyond 200cm. The power of lens  correct the vision will be :

  1. +0.5 D

  2. +5D

  3. -0.5D

  4. -5D
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Here, $u = \infty$ and $ v = -200\; cm$


$\Rightarrow \dfrac{1}{f} = \dfrac{1}{v} - \dfrac{1}{u}$

$\Rightarrow \dfrac{1}{f} =- \dfrac{1}{200} + 0$

$\Rightarrow f =-2m$
$\Rightarrow  P (in \; D)= \dfrac{1}{f(in\; m)} =- 0.5 D$

Therefore, C is correct option.

Multiple choice structure of human eye human eye and colourful world

The near point and the far point of a child are at 10 and 100 cm. If the retina is 2.0 cm behind the eyelens  .What is the range of the power of the eye lens?

  1. $50 D \text { to } 40 \mathrm { D }$
  2. $60 D \text { to } 51 \mathrm { D }$
  3. $60 D \text { to } 54 \mathrm { D }$
  4. $40 D \text { to } 50 \mathrm { D }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

\begin{array}{l} According\, \, to\, question................... \ Near\, point\, of\, the\, child\, (u)=10cm \ Far\, point\, of\, the\, child\, (u)=100cm \ and,the\, \, retina\, is\, \, \, 2\, cm\, behind\, the\, eye\, lens. \ \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, V=2\, cm=0.02\, m \ Now, \ \frac { 1 }{ f } =\frac { 1 }{ { 0.02 } } -\frac { 1 }{ { (-0.1) } } \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \left| { from\, lens\, formula:\frac { 1 }{ v } -\frac { 1 }{ u } =\frac { 1 }{ f }  } \right.  \ \, \, \, \, \, \, \, \Rightarrow 50+10=60\, m \ \therefore \, \, Power\, \, of\, the\, lens:\, \, P=\frac { 1 }{ f } =60\, D \ Now,\, \, \, consider\, the\, far\, point\, is\, \, 100\, cm. \ where, \ \, u=-100cm=-1m,\, \, \, and\, \, \, \, V=2\, cm=0.02\, m \ then, \ \frac { 1 }{ f } =\frac { 1 }{ { 0.02 } } -\frac { 1 }{ { (-1) } } \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \left[ { we\, have\, the\, lens\, formla: } \right. \frac { 1 }{ v } -\frac { 1 }{ u } =\frac { 1 }{ f }  \ \frac { 1 }{ f } =50+1=51\, m \ \therefore \, \, \, Power\, \, of\, the\, lens:\, \, P=\frac { 1 }{ f } =51\, D \ so,\, that\, the\, rangeof\, the\, \, power\, of\, eye\, lens\, is\, from\, \, \, \underline { 60\, D\, \, to\, \, 51\, D }  \ and\, the\, correct\, option\, is\, B. \ \, \,  \ so\, the\, correct\, optuon\, is\, A. \end{array}

Multiple choice structure of human eye human eye and colourful world

The hyperopic eye can be corrected using --- lens.

  1. concave

  2. convex

  3. plano convex

  4. plano concave
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Hyperopia or Far-sightedness is the condition where person can see the far objects clearly but cannot focus on near objects. This occurs since the image of nearby objects is formed behind retina. This corrected by using a convex lens which increases the power of the eye, and image is obtained on the retina.

Multiple choice structure of human eye human eye and colourful world

Which type of lens is used to treat myopia:

  1. Concave lens

  2. Convex lens

  3. Cylindrical lens

  4. Bifocal lens
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Near sightedness, or myopia, is the most common refractive error of the eye. Myopia occurs when the eyeball is too long, relative to the focusing power of the cornea and lens of the eye. This causes light rays to focus at a point in front of the retina, rather than directly on its surface. So, to treat myopia the glasses will be preceded by a minus sign ().
Hence, to treat myopia concave lens should be used.