Three index cards. A piece of modeling clay or sticky tack. You can also use double sided tape. A flashlight or a laser pointer. [2] X Expert Source Chris Hasegawa, PhDRetired Science Professor & Dean Expert Interview. 29 July 2021. A hole puncher. A ruler.
Take the hole puncher and punch a hole at the center of the card where the two lines intersect. Do this for the other two cards.
Form a stand for the cards using the clay so the cards are straight and upright. Use the ruler to ensure the cards are two to five inches from each other. You can also use double sided tape to attach the cards to a surface in a vertical position. Do not cover or obstruct the hole in the center of the cards with modeling clay or tape.
Note that the light can be seen through all the holes. You should be able to see the light go through all the holes and land on a wall or surface beyond the last index card.
Two to three sheets of black paper. A flashlight. [4] X Expert Source Chris Hasegawa, PhDRetired Science Professor & Dean Expert Interview. 29 July 2021. A small mirror. [5] X Expert Source Chris Hasegawa, PhDRetired Science Professor & Dean Expert Interview. 29 July 2021. Small objects like buttons, bottle caps, or dimes.
The other person will use the small mirror to reflect the flashlight so it hits the objects. Move close to the light, at an angle, to catch the light so it hits the objects. You may need to position more than one mirror to create a light path that shines on the objects. Play around with reflecting the light on the mirrors until the light hits the objects. You can also move the objects around the room to create a more complicated light path, using the flashlight as the light source. This experiment shows that light travels in a straight line in the air. But it also bounces off of a reflective surface, like a mirror. The angle of the light as it bounces off the mirror will be the same as the angle of the light as it hits the mirror. The mirror reflects the light and changes its path from a straight line to an angled straight line.
A large glass jar. Access to water. One cup of oil. A ruler. A spoon.
Make sure the jar is large enough to fit the ruler.
Note that the numbers appear stretched or magnified as the light rays bend in the oil and the water. Move the ruler from side to side to note the different appearances of the ruler numbers in the oil and in the water. This will show that light travels at different speeds in different mediums, such as air, oil, and water. It will travel in a straight line in the air, but it will bend when it changes speed due to contact with a certain medium, like oil or water.
