Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): When three thin lenses are placed in contact, the total magnification is the product of the magnifications produced by the separate lenses.
Reason (R): The image formed by the first lens acts as the object for the second lens, and the image formed by the second lens acts as the object for the third.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Both (A) and (R) are correct and (R) is the correct explanation of (A).
Assertion (A) When three thin lenses are placed in contact, the total magnification is the product of the magnifications produced by the separate lenses. — True. For lenses in contact, \( m=m_1m_2m_3 \).
Reason (R) The image formed by the first lens acts as the object for the second lens, and the image formed by the second lens acts as the object for the third. — True. Each lens forms its image of the image given by the lens before it.
Why Reason (R) explains Assertion (A)?
Let the object height be \(h\) and the image heights after the three lenses be \(h_1\), \(h_2\) and \(h^{\prime}\). Since each image is the next object, \(m_1=h_1/h\), \(m_2=h_2/h_1\) and \(m_3=h^{\prime}/h_2\).
Multiplying the three gives \( m_1m_2m_3=h^{\prime}/h \), the total magnification \(m\) of the combination.
NCERT (2026-27):
Combination of thin lenses in contact – “… Since the image formed by the first lens becomes the object for the second, … the total magnification m of the combination is a product of magnification (m1, m2, m3,...) of individual lenses”
\( \displaystyle m=m_1m_2m_3\ldots \qquad (9.33) \)