Question

In the figure shown the radius of curvature of the left & right surface of
the concave lens are 10 cm & 15 cm respectively. The radius of
curvature of the mirror is 15 cm. equivalent focal length of the
combination is :
(A) the system behaves like a convex mirror of focal length 18cm
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(B) the system behaves like a concave mirror of focal length 18cm
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(C) the system behaves like a convex mirror of focal length 36cm
(D) the system behaves like a concave mirror of focal length 36cm​

Answer 1

Answer:

my answer is the C) Answer

Answer 2

Answer

Peq=2PL1+2PL2+PM

=fL11+2(fL21)−fM1

Peq=−2(121)+454−(−152)

Peq=181

−f1=181

f=−18cm

Hence system act as concave mirror.