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an object of 4 cm is placed at a distance of 20cm from a concave lens of focal length 10cm. use lens formula to determine the position of the image formed.
Asked by archita123 | 21 Feb, 2016, 07:25: PM
answered-by-expert Expert Answer
Given that Object size, h = + 4 cm 
Object distance, u   = – 20 cm
Focal length, f = –10 cm
Image distance, v = ?Image size, h' = ? 
begin mathsize 12px style 1 over straight f equals 1 over straight v plus 1 over straight u or 1 over straight v equals space 1 over straight f minus 1 over straight u space space space space space space space space equals space fraction numerator 1 over denominator left parenthesis negative space 10 right parenthesis end fraction minus fraction numerator 1 over denominator left parenthesis negative 20 right parenthesis end fraction or 1 over straight v equals negative 1 over 20 space straight v space equals space minus 20 space cm The space screen space should space be space placed space at space 20 space cm space from space the space mirror. space The space image space is space real. space space Also comma space magnification comma space straight m space equals space fraction numerator straight h apostrophe over denominator straight h end fraction space equals space minus straight v over straight u space equals space minus fraction numerator left parenthesis negative 20 right parenthesis over denominator left parenthesis negative 20 right parenthesis end fraction space equals space minus 1 The space image space is space inverted space and space enlarged. space space space end style
Answered by Yashvanti Jain | 21 Feb, 2016, 11:20: PM

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