| Assertion (A): The focal length of a concave mirror is and an object is placed at a distance x from the focus. The magnification produced by the mirror is f/x. |
| Reason (R): magnification = size of image / size of object |
A) Both A and R are true and R is the correct explanation of A
B) Both A and R are true but R is NOT the correct explanation of A
C) A is true but R is false
D) A is false and R is True
Correct Answer: A
Solution :
| Option [a] is correct. |
| Explanation: Using mirror formula, |
| 1/v+1/u=1/f |
| Or, 1/v - 1/(f+x)=-1/ |
| \[\therefore \ v=-f(f+x)/x\] |
| Magnification (m) = size of image / size of object = - v/u |
| \[[m]=\frac{f(f+x)}{x}\times \frac{1}{f+x}=f/x\] |
| So, the assertion and reason both are true and the reason properly explains the assertion. |
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