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Light Reflection and Refraction
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24/08/2021 12:07 pm
Topic starter
The power of a combination of two lenses X and Y is 5 D. If the focal length of lens X be 15 cm :
(a) calculate the focal length of lens Y.
(b) state the nature of lens Y.
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24/08/2021 12:11 pm
(a) P = Px + PY
P = \(\frac{1}{f_x}\) + \(\frac{1}{f_Y}\)
5 = \(\frac{100}{15}\) + \(\frac{1}{f_Y}\)
\(\frac{1}{f_Y}\) = 5 - \(\frac{100}{15}\)
= \(\frac{-25}{15}\)
\(f_Y\) = -0.6 m = -60 cm
(b) Lens Y is a concave lens since it has negative focal length.