Convex lenses and where images form

Answer Key - Grade 11 Science Worksheet - Building Confidence

Circle the best answer, or write your answer on the line.

1. 1.

   A toy 1.5 cm tall stands 40 cm from a convex lens, and its sharp image forms 20 cm on the other side. How tall is the image, Esme?

   0.75 cm

2. Read this first

   Ray diagram (example data)

   a convex lens with a focal length of 10 cm. A toy 2 cm tall stands 30 cm in front of it. Three principal rays leave the toy's top: one parallel to the axis bends through the far focal point; one through the lens center goes straight; one through the near focal point leaves parallel. They meet 15 cm beyond the lens, where an image 1 cm tall forms upside down.

3. 2.

   In the ray diagram, how far from the lens does the image form, Jun?

   • 10 cm, at the focal point
   • 30 cm, where the toy is
   • 15 cm, on the far side
4. 3.

   In the ray diagram, which way up is the image, Kira?

   • Upside down
   • Sideways
   • The right way up
5. 4.

   In the ray diagram, could a screen placed 15 cm beyond the lens show the image, Luz?

   • No: it is a virtual image
   • No: lenses don't make images
   • Yes: it is a real image
6. 5.

   A ray from the toy travels parallel to the lens's axis. Where does it go after the lens, Milo?

   • Back toward the toy
   • Through the far focal point
   • Straight on, parallel
7. 6.

   A ray from the toy passes through the very center of the lens. What does it do, Noah?

   • Bends through the focal point
   • Goes straight on without bending
   • Reflects back
8. 7.

   A ray from the toy passes through the near focal point before the lens. How does it leave the lens, Pia?

   • Through the far focal point
   • Parallel to the axis
   • Straight back
9. 8.

   A magnifying glass is held so a stamp is closer to it than its focal length. What image is seen, Ren?

   • The same size and real
   • Larger, upright and virtual
   • Smaller, upside down and real
10. 9.

    A camera lens forms an image of a distant tree on its sensor. What is the image like, Tala?

    • The same size as the tree
    • Large, virtual and upright
    • Small, real and upside down
11. 10.

    A projector puts a small slide just beyond the lens's focal point. What image does it throw on the screen, Zee?

    • Small, real and upright
    • Virtual, so no image on the screen
    • Large, real and upside down