Question

a compound lens is made if two lenses having power +15.5D and -5.5D. an object 3cm of height is placed at a distance of 30cm. from this compound lens find out the size of the image​

Answer 1

Answer:

Here, The size of the image is 3.09cm.

Explanation:

Here, As per our given question,

=Total power of the compound lens=15.5D+(-5.5D)

=15.5-5.5

=15D is the Total power.

Now,We have to find out focal length(f)=

=P=1/f

=15=1/f

=15f=1

=f=1/15

=f=0.67 cm

Now, Distance of the image from the mirror,

=1/V-1/U=1/f (Where, U=distance of the object)

=1/V=1/f+1/U

=1/V=1/0.67+1/30

Now, by doing reciprocal in it, we get,

=V=0.67+30

=V=30.67 cm

Now, As it is considered that,

(Magnification)M=V/U,

=M=30.67/30

=M=1.03

Now, height of image=M=hi/ho (Where, hi=height of image, ho=height of object)

=1.03=hi/3

=hi=1.03×3

=hi=3.09 cm (Answer).

Thank you.