Some Physics questions! Almost finished school!?

Question

A rod length 5.0 cm lies along the axis of a concave mirror of radius of curvature 20 cm. The end of the rod closer to the mirror is 15 cm from the mirror. Find the length of the image of the rod.

A. 10 cm

B. 20 cm

C. 30 cm

D. 40 cm

An obect of height 4 cm is placed at a distance of 20 cm from a convex lens of focal length 10 cm. Find the nature of the image.

A. virtual, enlarged

B. virtual, inverted

C. real, enlarged

D. real, inverted

Now guys, please bear in mind that my book is VERY vague, so if one or both of the questions are to vague, I apologize, but I could use this as soon as possible! Thanks for all of your help!

Answer 1

Use the lens formula for the lens with f=+10cm for the position of each end of the rod:

1/X = 1/10 - 1/15  gives x = 30cm

1/X = 1/10 - 1/20  gives x = 20cm

length of image = 30 - 20 = 10cm

part 2

if the object distance is 2f the image distance will be 2f

so answer is D.

or use the lens formula to show the image is real and the same distanceaway fro the lens so the same size.