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MHT CET 2026 (15 May, Shift 1) · Prism, Dispersion & Scattering

Prism, Dispersion & Scattering question from MHT CET 2026 (15 May, Shift 1)

Q16MHT CET 2026 · 15 MAY · SHIFT 1Medium

Prism, Dispersion & Scattering

An achromatic convergent doublet of two lenses in contact has a power of +2D+2D. The convex lens has power +5D+5D. What is the ratio of the dispersive powers of the convergent and divergent lenses?

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Answer: (b)

  1. Lenses in contact: P=P1+P2⇒2=5+P2⇒P2=−3 DP = P_1 + P_2 \Rightarrow 2 = 5 + P_2 \Rightarrow P_2 = -3\,D.
  2. Achromatism: ω1P1+ω2P2=0⇒ω1ω2=−P2P1\omega_1 P_1 + \omega_2 P_2 = 0 \Rightarrow \dfrac{\omega_1}{\omega_2} = -\dfrac{P_2}{P_1}.
  3. ω1ω2=35\dfrac{\omega_1}{\omega_2} = \dfrac{3}{5}
  4. So the answer is (b) 3:53 : 5.
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