Optics Ques 81
- A parallel beam of white light fall on a combination of a concave and a convex lens, both of the same material. Their focal lengths are $15 cm$ and $30 cm$ respectively for the mean wavelength in white light. On the same side of the lens system, one sees coloured patterns with violet colour nearer to the lens.
$(1988,2 M)$
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Answer:
Correct Answer: 81.$T$
Solution:
Formula:
- Focal length of concave is less, i.e. power of concave lens will be more. Hence, the combination will behave like a concave lens. Further, $\mu _V$ is greater than all other colours. Hence, $f _V$ will be least.
BETA
