How to calculate the weight of a pencil of mass 5g​

How does the image distance (di) of a convex lens compare with the image distance of a concave lens? a. the image distance of the convex lens is positive, and that of the concave lens is negative. b. both are negative for a virtual image. c. both are positive for a virtual image d. the image distance of the convex lens is negative, and that of the concave lens is positive.

What are chlorofluorocarbons and what impact do they have on the atmosphere?

Which transition by an electron will release the greatest amount of energy? oa ob oc od