Class 10ScienceThe Human Eye and the Colourful WorldMix Examples - The Human Eye and the Colourful World
MediumWhat are hypermetropia and myopia? What are their causes? How are they rectified?
(N/A) These are common defects of vision.
Hypermetropia (Farsightedness): $A$ person suffering from this defect can see distant objects clearly but cannot see nearby objects clearly. In this defect,the near point of the eye shifts farther away than $25 \ cm$.
Causes:
$1.$ The eyeball becomes too short.
$2.$ The focal length of the eye lens becomes too large.
Correction: This condition is corrected using a converging or convex lens.
Myopia (Nearsightedness): $A$ person suffering from myopia can see nearby objects clearly but cannot see distant objects clearly. In this defect,the far point of the eye comes closer than infinity.
Causes:
$1.$ The eyeball becomes too long.
$2.$ The focal length of the eye lens becomes too small.
Correction: This condition is corrected using a diverging or concave lens.
Hypermetropia (Farsightedness): $A$ person suffering from this defect can see distant objects clearly but cannot see nearby objects clearly. In this defect,the near point of the eye shifts farther away than $25 \ cm$.
Causes:
$1.$ The eyeball becomes too short.
$2.$ The focal length of the eye lens becomes too large.
Correction: This condition is corrected using a converging or convex lens.
Myopia (Nearsightedness): $A$ person suffering from myopia can see nearby objects clearly but cannot see distant objects clearly. In this defect,the far point of the eye comes closer than infinity.
Causes:
$1.$ The eyeball becomes too long.
$2.$ The focal length of the eye lens becomes too small.
Correction: This condition is corrected using a diverging or concave lens.
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What is the near point of a normal human eye (in $cm$)?
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$(a)$ Draw ray diagrams to illustrate the formation of image of the blackboard writing by his eye lens when he is seated at the $(i)$ last desk,$(ii)$ front desk.
$(b)$ Name the defect of the eye from which the student is suffering.
$(c)$ Name the kind of lens that would help him to see clearly even when he is seated at the last desk. Draw a ray diagram to illustrate how this lens helps him to see clearly.
$(a)$ Draw ray diagrams to illustrate the formation of image of the blackboard writing by his eye lens when he is seated at the $(i)$ last desk,$(ii)$ front desk.
$(b)$ Name the defect of the eye from which the student is suffering.
$(c)$ Name the kind of lens that would help him to see clearly even when he is seated at the last desk. Draw a ray diagram to illustrate how this lens helps him to see clearly.
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$(b)$ Which colour of light bends least and which one the most while passing out from the prism? Also,state the reason for the same.
$(b)$ Which colour of light bends least and which one the most while passing out from the prism? Also,state the reason for the same.
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View Solution$A$ person cannot see objects distinctly when placed at a distance less than $50\, cm$.
$(a)$ Identify the defect of vision.
$(b)$ Give two reasons for this defect.
$(c)$ Calculate the power and nature of the lens he should be using to see clearly the object placed at a distance of $25\, cm$ from his eyes.
$(d)$ Draw the ray diagrams for the defective and the corrected eye.
$(a)$ Identify the defect of vision.
$(b)$ Give two reasons for this defect.
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