Home Page Textbooks Nelson Science Perspectives 10 Section 13-6: The Human Eye

Nelson Science Perspectives 10

1st Edition

Christy C. Hayhoe, Doug Hayhoe, Jeff Major, Maurice DiGiuseppe

ISBN: 9780176355289

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Section 13-6: The Human Eye

Exercise 1

Solution 1

Solution 2

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Both human eye and camera have converging lens which focuses rays of light into one single point.

Both human eye and camera both have screen at the back where real image is formed by converging length. Screen in the human eye is retina and screen in the camera is either photographic film or charged couple device.

They are both capable of focusing a sharp image of the object which is manually done in the case of camera and which is controlled by eye muscles in the case of human eye.

Result

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Both human eye and camera have converging lens, screen and are capable of focusing sharp image, but in the case of human eye screen is the retina and focusing is controlled by eye muscles and in the case of camera screen is either photographic film or charged couple device and focusing is controlled manually.

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The human eye and a camera both have a converging lens that collects the light from its surroundings.

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The human eye and a camera both have a screen at the back where the real image formed by the converging lens is displayed. In human eye this screen is the retina while in a camera this screen can be a photographic film or charged couple device.

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The human eye and a camera both are capable of focusing a sharp image of the object on their respective screens. In the human eye this operation is controlled by eye muscles while in a camera this is manually done by the photographer.

Exercise 2

Solution 1

Solution 2

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The image produced by the eye lens on the retina is real in nature and therefore inverted in attitude. The brain is specially designed to invert this real image to an upright position so that the human eye sees objects as they are and not inverted and therefore the statement that “see with our brains”, hold true because accurate images of our surroundings are in fact produced by the brain and not the eye.

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Image which is produced by the eye lens is real and inverted in attitude.

Brain inverts this real image into the upright position because of which we are capable to see objects as they truly are which explains the statement “see with our brain” since the truly image of an object is formed by the brain not the eye.

Result

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What explains the statement is that the image which is formed by the human eye is real, but inverted and what helps us see the true image of the object is the brain, which makes the image upright.

Exercise 3

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a.
$color{#c34632}text{Far}$-sightedness is an eye problem in which the person suffering from it is able to $color{#c34632}text{clearly}$ see $color{#c34632}text{distant}$ objects but is unable to see close objects clearly.

$color{#4257b2}text{Near}$-sightedness is an eye problem in which the person suffering from it is able to $color{#4257b2}text{clearly}$ see $color{#4257b2}text{close}$ objects but is unable to see distant objects clearly.

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$color{#c34632}text{Far}$-sightedness can be corrected using a $color{#c34632}text{converging lens}$ while $color{#4257b2}text{near}$-sightedness can be corrected using a $color{#4257b2}text{diverging lens}$.

Result

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Exercise 4

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$color{#c34632}text{Far}$-sightedness is now corrected using a $color{#c34632}text{positive meniscus lens}$. It is a modified version of the basic converging lens. It is still a converging lens but thinner and therefore more beautiful to wear (in glasses). It is also lighter in weight and therefore easier to wear and does not leave glasses marks on nose.

Step 2

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$color{#c34632}text{Near}$-sightedness is now corrected using a $color{#c34632}text{negative meniscus lens}$. It is a modified version of the basic diverging lens. It is still a diverging lens but thinner and therefore more beautiful to wear (in glasses). It is also lighter in weight and therefore easier to wear and does not leave glasses marks on nose.

Result

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Exercise 5

Solution 1

Solution 2

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a. People require reading glasses as they get older because of far-sightedness also known as hyperopia. This is caused by the shrinking of the eye ball, such that the lens is unable to focus the image on the retina, rather does it behind the retina. As a result the image is formed behind the retina and therefore blurred.

Step 2

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b. A positive meniscus lens is used to correct hyperopia. This lens converges the light ray inwards on to the eye lens so that the image is formed on the retina.

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$textit{a.}$, People require reading glasses as they get older because of the farsightedness (hyperopia) which is caused by the shrinking of the eyeball which makes lens unable to focus the image on the retina; focusing happens behind the retina.

Image which is formed behind it is blurred.

Step 2

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$textit{b.}$, Hypeporia is correct by the positive meniscus lens, converging lens which converges ray of light inwards on so that the image can be formed in retina.

Result

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$textit{a.}$, Because as we get older our eyeball is shrinking and lens is unable to focus image on the retina, it does behind it instead so the image which is formed is blurry.

$textit{b.}$, This can be fixed by converging lens.

Exercise 6

Solution 1

Solution 2

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When a beam of light from the sun is converged on to a single point using a converging lens, it is hot enough to light up a fire. This is a typical property of converging lens or positive meniscus lens as they converge light. Near-sightedness is however corrected using a diverging or negative meniscus lens and therefore glasses of near-sightedness can not be used for this purpose.

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Beam of light converged into a single point by a converging lens will make that point hot enough so the fire can be lit up.

This is a typical property of converging lenses since they converge light.

Nearsightedness is corrected by using a diverging lens, therefore, glasses of this type cannot be used for that purpose.

Result

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$textit{a.}$, Fire can be lit up by the converging lens since it converges beam of light into one single point, therefore, glasses for nearsightedness which are made of diverging lenses which diverge beam of light cannot be used for this particular purpose.

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Section 13-6: The Human Eye

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