Assertion (A): In displacement method of finding focal length of a convex lens, if magnification in a position of lens is \( -2 \), then magnification in another position of lens should be \( -1/2 \).
Reason (R): This method can not be applied for diverging lens.
Both (A) & (R) are true and the (R) is the correct explanation of the (A)
Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(A) is true but (R) is false
Both (A) and (R) are false
Solution:
In the displacement method, if magnifications are \( m_1 \) and \( m_2 \) for two positions, then \( m_1 m_2 = 1 \). If \( m_1 = -2 \), then \( m_2 = -1/2 \). The method requires formation of real images, which diverging lenses cannot produce for real objects.
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