A 2.26 cm tall object is placed in 18.6 cm in front of a convex lens. The focal length
is 35.8 cm. How far is the image from the lens?

the image is -38.7 cm from the lens

Explanation:

We use the lens equation which says  

where is the distance to the object, is the distance to the image, and  is the focal length.

Now, in our case

,

,

;

therefore,

where the negative sign indicates that the image is virtual and on the same side of the lens as the object.

electrical potential energy =0.072 j

explanation:

electrical potential energy is given by

u= q δv

q= charge=6 c

δv= potential difference and is given by

δv= e d

e= electric field

d= distance=5 mm=0.005 m

δv=2.4 (0.005)=0.012 v

now electric potential energy= u= q δv

u=6 (0.012)

u=0.072 j