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  a) The image formed in front of the concave mirror is real, so m is negative,   m = -3, u = -10 cm   As m = -v/u or -3 = -v/-10 v = -30 cm   By mirror formula,   1/f = 1/v + 1/u = 1/-30 + 1/-10 = -4/30   or f = -30/4 = -7.5 cm  Radius of curvature, R = 2f = 2 x (-7.5) = 15cm   a) The image formed in front of the concave mirror is real, so m is negative,   m = -3, u = -10 cm   As m = -v/u or -3 = -v/-10 v = -30 cm   By mirror formula,   1/f = 1/v + 1/u = 1/-30 + 1/-10 = -4/30   or f = -30/4 = -7.5 cm  Radius of curvature, R = 2f = 2 x (-7.5) = 15cm           the above answer is wrong pls check it  
Asked by prithivan2005 | 03 Apr, 2020, 02:33: PM
answered-by-expert Expert Answer

a) The image formed in front of the concave mirror is real, so m is negative,

 m = -3, u = -10 cm

 As m = -v/u or

-3 =- v/-10

v = -30 cm  

By mirror formula,

 1 over f equals 1 over v plus 1 over u 1 over f equals fraction numerator 1 over denominator negative 30 end fraction plus fraction numerator 1 over denominator negative 10 end fraction space rightwards double arrow f equals space minus space 7.5 space c m space

Thus, focal length of concave mirror is 7.5 cm. 

 Thus, Radius of curvature, R = 2f = 2 x (-7.5) = - 15cm

 Negative sign indicates that the mirror is concave mirror. 

The calculations seems to be perfect. And it follows all the conditions as per the given data. If you still have any doubt regarding it you can post the complete question which will give clear idea about what information is actually given and what needs to be calculated. 
 
As the object is placed at 10 cm it means it is between centre of curvature and focus and hence the image must be formed beyond centre of curvature i.e. 30 cm according to given data. 
 



Answered by Shiwani Sawant | 03 Apr, 2020, 03:33: PM

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