関連ワード:
focal length in concave lens is always negative focal length in concave lens is positive or negative focal length in concave mirror is always negative focal length in concave mirror is always negative or positive focal length in concave lens is always positive or negative focal length in convex lens is positive or negative focal length in concave mirror is positive or negative focal length in convex lens is always positive or negative focal length in convex mirror is positive or negative focal length in concave and convex lens is positive or negative
