Which are mixtures ?

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 atoms of the same element with varying number of neutrons

Determine the age of a fossil if it had only one eighth of its original carbon-14 content remaining?