Plane mirrors and the law of reflection

Answer Key - Grade 11 Science Worksheet

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

1. 1.

   A flashlight 3 m up bounces a beam off a floor mirror onto a target 1 m up, 8 m away across the floor. How far from the flashlight's foot is the bounce point, Ari?

   6 m
2. 2.

   A flashlight 4 m up bounces a beam off a floor mirror onto a target 1 m up, 10 m away across the floor. How far from the flashlight's foot is the bounce point, Esme?

   8 m
3. 3.

   Two plane mirrors face each other 0.6 m apart. A lamp is 0.2 m from the first. The second mirror reflects the first image. How far from the lamp is that new image, Jun?

   • 2.4 m, twice the answer for the first image
   • 1.2 m, twice the 0.6 m gap
   • 0.6 m, the gap between the mirrors
   • 0.8 m, the lamp's image in the second mirror
4. 4.

   A periscope has two parallel mirrors at 45°, 1.2 m apart along the tube. A horizontal beam enters the top. What does Kira see leaving the bottom?

   • A horizontal beam going the same way, 2.4 m lower
   • A horizontal beam going the same way, 1.2 m lower
   • A horizontal beam going back the way it came
   • A vertical beam, because the tube is vertical
5. 5.

   A camera on top of a 1.8 m pole must see the whole pole in a wall mirror. Luz moves the pole from 2 m to 4 m away. What mirror height is needed?

   • 0.9 m at both distances, half the pole's height
   • 0.45 m at 4 m: farther objects look smaller
   • 1.8 m at both distances, the pole's full height
   • 1.8 m at 4 m: the pole is twice as far
6. 6.

   Two mirrors meet at 50°. A beam reflects once off each. Through what angle has Noah's beam turned from its original direction?

   • 100°, twice the angle between the mirrors
   • 50°, the angle between the mirrors
   • 130°, the supplement of the angle between the mirrors
   • 80°, 180° − 100°
7. 7.

   A lamp sits between two hinged mirrors set 60° apart. How many images of the lamp does Pia's camera see?

   • 2 images, one in each mirror
   • 5 images: 360° ÷ 60° − 1
   • 6 images: 360° ÷ 60°, forgetting to remove the lamp itself
   • 3 images, the number for mirrors at 90°
8. 8.

   Ren's drone flies straight at a wall mirror at 2 m/s. How fast does the drone approach its own image?

   • 0 m/s, because a virtual image is not really there to meet
   • 4 m/s, because the image also approaches at 2 m/s
   • 1 m/s, half the drone's speed, shared with the image
   • 2 m/s, the drone's own speed, with the image ignored
9. 9.

   A drone hovers in front of a wall mirror. Tala pushes the mirror toward the drone at 0.5 m/s. How fast does the drone's image move?

   • 1.0 m/s toward the drone, twice the mirror's speed
   • 0 m/s, because the drone is still
   • 0.25 m/s toward the drone
   • 0.5 m/s toward the drone, the same as the mirror's speed
10. 10.

    A reflected beam hits a wall 3.0 m away at right angles. Zee turns the mirror 22.5°. How far does the spot move along the wall?

    • 1.5 m: half the wall distance
    • 1.24 m: tan 22.5° × 3.0 m, using the mirror's turn
    • 3.0 m: the beam turns 45°, and tan 45° = 1
    • 6.0 m: twice the wall distance