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Wave Optics

Question

A thin glass (refractive index 1.5) lens has an optical power of – 5D in air. Its optical power in a liquid medium with refractive index 1.6 will be

1 D

5/8 D

-1 D

25 D

Solution

5/8 D

straight P subscript straight m over straight P subscript air space equals space fraction numerator open parentheses begin display style straight mu subscript calligraphic l over straight mu subscript straight a minus 1 end style close parentheses over denominator open parentheses begin display style straight mu subscript calligraphic l over straight mu subscript straight m minus 1 end style close parentheses end fraction straight P subscript straight m space equals space 5 divided by 8 space straight D