Question

Two thin lenses 3D and -2D are placed in contact ,then power ,then power and focal length of the combination is 

+2D ,+100 cm

+1D,+100 cm

+5 D,+20 cm

+1D, -100cm​

Answer 1

Answer:

+1D, +100cm

Explanation:

P=P1+P2

P=3-2

P=+1D

1/F=P

1/F=1D

1/F=100cm. (1D=100cm)

Answer 2

Power=+1D

Focal length=100 cm