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  • Rishi went to a palmist to show his palm. The palmist used a special lens for this purpose. (i) State the nature of the lens and reason for its use. (ii) Where should the palmist place/hold the lens so as to have a real and magnified imag

Rishi went to a palmist to show his palm. The palmist used a special lens for this purpose.
(i) State the nature of the lens and reason for its use.
(ii) Where should the palmist place/hold the lens so as to have a real and magnified image of an object ?
(iii) If the focal length of this lens is 10 cm and the lens is held at a distance of 5 cm from the palm, use lens formula to find the position and size of the image.

 

 

 

 
 
 
 
 

Answers (1)

(i) State the nature of the lens and reason for its use.
(ii) Where should the palmist place/hold the lens so as to have a real and magnified image of an object ?
(iii) If thse focal length of this lens is 10 cm and the lens is held at a distance of 5 cm from the palm, use len formula to find the position and size of the image.

(i) Nature of lens will be Convex lens to get a magnified image of the lines on the palm.

(ii) It should be between F and 2F of the lens / or at F of the lens

(iii) Given ,

   focal length f = +10 cm and

  object distance u = -5 cm

Lens formula 1./ v − 1/ u = 1/ f

1/ v − 1/ −5 = 1/ 10

1/ v + 1/ 5 = 1/ 10

1/ v = 1/ 10 − 1/ 5 = 1−2 /10

1/ v = −1/ 10

v = −10 cm 

m = himage/ hobject

  = v/ u

= −10/ −5

= 2

Therefore, the Size of image is 2 times the size of object.

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Safeer PP

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