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  • (a) A security mirror used in a big showroom has radius of curvature 5 m. If a customer is standing at a distance of 20 m from the cash counter, find the position, nature and size of the image formed in the security mirror. (b) Neha visited a de

(a) A security mirror used in a big showroom has radius of curvature 5 m. If a customer is standing at a distance of 20 m from the cash counter, find the position, nature and size of the image formed in the security mirror.
(b) Neha visited a dentist in his clinic. She observed that the dentist was holding an instrument fitted with a mirror. State the nature of this mirror and reason for its use in the instrument used by dentist.

 

 

 

 
 
 
 
 

Answers (1)

(a) It is a convex mirror.So focal length should be positive

 Radius of curvature R= + 5 m

∴ focal length f = 5/ 2 = +2.5 m

Object distance u= -20m

Mirror formula 1/v + 1/ u = 1/ f

1/ v + 1/ −20 = 1/ 2.5 1

v = 1/ 20 + 1/ 2.5

1/ v = 1/ 20 + 10/ 25

1/ v = 5+ 40 / 100 = 45/ 100

v = 100/ 45 = 20/ 9 = +2.2m

Therefore the Nature of image = virtual and erect image

and the Size of image : diminished image

 

(b) The nature of this mirror is Concave Mirror because it is used to obtain erect and enlarged image of teeth

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Safeer PP

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