For dispersion without deviation: $\delta_1 + \delta_2 = 0$
$$(\mu_1 - 1)A_1 = (\mu_2 - 1)A_2$$
$$(0.5)(6°) = 3° \quad \text{and} \quad (0.75)(4°) = 3°$$
Since deviations are equal, placing prisms in opposition achieves zero net deviation.
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JEE Main 2022 — Physics Optics
medium
mcq
2022
Official previous-year question
Verified 30 May 2026.
Question
A thin prism of angle $6°$ and refractive index $1.5$ is combined with another prism of angle $4°$ and refractive index $1.75$ to produce dispersion without deviation. This is:
Options
- A
Not possible with given values
- B
Possible if placed in opposition
- C
Possible only with a third prism
- D
Possible only in liquid medium
Solution
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