Plane mirrors and the law of reflection

Answer Key - Grade 11 Science Worksheet - Building Confidence

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

1. 1.

   A beam reflects off a flat mirror. Esme turns the mirror 12° about its hinge while the incoming beam stays put. By how many degrees does the reflected beam turn?

   24 °
2. 2.

   Jun measures 100° between a beam and its reflection off a flat mirror. What angle does the incoming beam make with the mirror's surface?

   • 130°: the supplement of the 50° from the normal, 180° − 50°
   • 40°: 50° from the normal, so 40° from the surface
   • 50°: half of the 100° between the beams, which is from the normal
   • 80°: the supplement of the 100° between the beams, 180° − 100°
3. 3.

   The incoming and reflected beams at a flat mirror are at right angles to each other. What angle does the incoming beam make with the mirror's surface, Kira?

   • 22.5°: half of the 45° that each beam makes with the normal
   • 135°: the supplement of the 45° from the normal, 180° − 45°
   • 45°: each beam is 45° from the surface too
   • 90°: the full angle between the two beams, not half of it
4. 4.

   A beam meets a mirror 35° from the normal. Luz tilts the mirror so it meets the beam 50° from the normal. How does the angle between the rays change?

   • It grows from 35° to 50°, as if the rays were 35° and 50° apart
   • It grows from 70° to 130°, as if the rays were 180° − 50° apart
   • It grows from 70° to 100°, a gain of 30°
   • It grows by 15°, the change in the angle from the normal
5. 5.

   A lamp stays still in front of a plane mirror. Milo slides the mirror 0.5 m toward the lamp. How far does the lamp's image move?

   • 0 m, because the lamp did not move, so its image stays put
   • 0.25 m toward the lamp, half of the mirror's own move
   • 1.0 m toward the lamp, twice as far as the mirror moved
   • 0.5 m toward the lamp, the same distance the mirror moved
6. 6.

   A lamp is 1.5 m from a plane mirror. A camera is 2.5 m from the mirror, on the same line. How far should Noah focus the camera to photograph the lamp's image?

   • 4.0 m: 2.5 m to the mirror plus 1.5 m behind it
   • 5.5 m: 2.5 m + 1.5 m + 1.5 m
   • 2.5 m: the camera's distance from the mirror, not the image
   • 1.0 m: the gap between the camera and the lamp
7. 7.

   An arrow card in front of a plane mirror points straight at the mirror. Pia looks at its image. Which way does the image arrow point?

   • Sideways, because the mirror swaps left and right
   • Away from the mirror, the same way as the card's own arrow
   • Toward the mirror, so the two arrows point at each other
   • Nowhere, because a virtual image has no direction
8. 8.

   Ren puts a white screen where a plane mirror's image appears, behind the glass. Why does no image show on the screen?

   • No light goes there; it only seems to come from that spot
   • The image is too dim to show up on a plain white screen
   • The glass takes in the light before it reaches the screen
   • The mirror is too smooth to send any light to that spot behind it
9. 9.

   A 0.3 m tall lamp stands 3 m in front of a plane mirror. How tall is its image, and how far is it from the lamp, Tala?

   • 0.6 m tall, 6 m from the lamp
   • 0.3 m tall, 6 m from the lamp
   • 0.3 m tall, 3 m from the lamp
   • 0.15 m tall, 6 m from the lamp
10. 10.

    A camera sees a lamp's image in a plane mirror. Zee draws the light's real path. Which drawing is right?

    • Lamp to the camera in a straight line, ignoring the mirror
    • Lamp to mirror to camera; the line to the image is dashed
    • From the image behind the glass to the camera in a straight line
    • From the camera to the mirror, where the light stops