Question

6. Two lenses with focal length 20 cm and -10 cm are placed together. Determine the power of combination​

Answer 1

ACCORDING TO THE EQUATION

20CM(-10)CM

20/-10CM

=4/2CM

=-2CM IS THE ANSWER

Answer 2

Answer:

-5D

Explanation:

1/feq=1/f1+1/f2  So, 1/feq=1/20-1/10 this is equals to feq=-20 cm  

Power = 1/feq

where f is in meters

so in meters feq=-20/100      

power=1/-20/100

=-5D