Using the State Curriculum: Science, Grade 5

Light travels in a straight line

Use a laser pointer or flashlight to demonstrate that light travels in a straight line.

• Ask a student to hold the laser or flashlight parallel to the floor so the beam travels across the front of a darkened room.
• Ask another student to clap two chalk-covered erasers together or sprinkle fine talcum powder along the path of the light beam.
• Students should see the straight beam of light reflected from the particles in the air.

Safety issue: Caution students to avoid looking directly into the beam of the laser.

Light reflects from a plane mirror

A laser pointer and chalk dust or talcum powder can also be used to demonstrate reflection from a plane mirror.

• Position the mirror in the front of the room above the heads of seated students.
• Ask a student to hold the laser pointer at an angle to the mirror and parallel to the floor.
• Ask students to predict the path of the beam after it reflects from the mirror.
• Turn on the laser and shine the beam toward the mirror while two other students add chalk dust or talcum powder along the path of the light beam, one toward the mirror and the other away from the mirror.
• Compare the predicted angle with the actual angle of reflection.
• Use a large protractor to measure the incoming angle (angle of incidence) and the angle of reflection.

Safety issue: Caution students to avoid looking directly into the beam of the laser.