Math, asked by wwwsunnymanwar456cc, 10 hours ago

39. Two thin lenses, one of focal length +60 cm and the other of focal length -20 cm are kept in contact. Their combined focal length is (a) Minus 30 cm (b) Plus 30 cm (c) Minus 15 cm (d) Plus 30 cm

Answers

Answered by sharonthomas28

0

Answer:

Combined focal length,

1/f=1/fdown 1 +1/f down 2

1/f=1/60-1/20

f= -30 cm

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