Question

two lenses of powers 4D and 5D are in contact find the focal length of the combination what is the nature of the combination​

Answer 1

hey there!!!

here, power of two lenses= 4D and 5D

hence,

combined power= 4D+5D= 9D.

now,

we know,

power= 1/f(m)......f= focal length.

therefore,

9= 1/f

f= 1/9= 0.11m

here,

resultant power= +9D

hence,

the nature of the combination is positive.

hope this helps!! ❤✌☺