1
KCET 2021
+1
-0

Two thin biconvex lenses have focal lengths $$f_1$$ and $$f_2$$. A third thin biconcave lens has focal length of $$f_3$$. If the two biconvex lenses are in contact, then the total power of the lenses is $$P_1$$. If the first convex lens is in contact with the third lens, then the total power is $$P_2$$. If the second lens is in contact with the third lens, the total power is $$P_3$$, then

A
$$P_1=\frac{f_1 f_2}{f_1-f_2}, P_2=\frac{f_1 f_3}{f_3-f_1}$$ and $$P_3=\frac{f_2 f_3}{f_3-f_2}$$
B
$$P_1=\frac{f_1-f_2}{f_1 f_2}, P_2=\frac{f_3-f_1}{f_3+f_1}$$ and $$P_3=\frac{f_3-f_2}{f_2 f_3}$$
C
$$P_1=\frac{f_1-f_2}{f_1 f_2}, P_2=\frac{f_3-f_1}{f_1 f_3}$$ and $$P_3=\frac{f_3-f_2}{f_2 f_3}$$
D
$$P_1=\frac{f_1+f_2}{f_1 f_2}, P_2=\frac{f_3-f_1}{f_1 f_3}$$ and $$P_3=\frac{f_3-f_2}{f_2 f_3}$$
2
KCET 2021
+1
-0

The size of the image of an object, which is at infinity, as formed by a convex lens of focal length $$30 \mathrm{~cm}$$ is $$2 \mathrm{~cm}$$. If a concave lens of focal length $$20 \mathrm{~cm}$$ is placed between the convex lens and the image at a distance of $$26 \mathrm{~cm}$$ from the lens, the new size of the image is

A
1.25 cm
B
2.5 cm
C
1.05 cm
D
2 cm
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Medical
NEET