What colors form the spectrum of visible light?

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.

Will you chech and finish these for me, because i am stumped with them.

Clothes dryer uses about 7 amps of current from a 240 volt line. how much power does it use?