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  • (a) A student is unable to see clearly the words written on the black board placed at a distance of approximately 3 m from him. Name the defect of vision the boy is suffering from. State the possible causes of this defect and explain the method of corr

(a) A student is unable to see clearly the words written on the black board placed at a distance of approximately 3 m from him. Name the defect of vision the boy is suffering from. State the possible causes of this defect and explain the method of correcting it.

(b) Why do stars twinkle ? Explain.

 

 

 

 
 
 
 
 

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(a) The boy is suffering from near sightedners i.e, Myopia. The possible cause of this defect are elongation of eyeball excessive curvature of eye lens . This defect can be corrected by placing concave lens in front of eye.

(b) Stars emit light on their own when this light travels through earth's atmosphere which has variable opticle density .the continuosly changing atmosphere refracts the amount from stars in different amount from one moment to next .The light seem to be bright and as it keeps changing because of continuous refraction through different layers of atmosphere of earth.Hence, we say light twinkles at night.

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Sumit Saini

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