Objective:
Visible light is not monochromatic but it is composed of seven colors which splits up to component colors when sunlight is incident on transparent objects like prism. Sir Isaac Newton showed this fact for the first time with the help of a disc called Newton’s Disc in which the seven colors of the visible white light is arranged.
Activity for Light Lesson Plans
Materials:
Light source
Prisms
White cardboard sheet
Spectrometer
Procedure: Begin your class by asking students about the color of visible light. Instruct them to watch the following activity and arrive at a conclusion of their own.
- Arrange the prism in a table and place the white board in the opposite side of the prism. Keep the room completely dark. Allow light from a source to fell on the prism and properly set the white board so that the seven colors are visible in the board. But the colors will not be distinctively separated. So teachers can make use of spectrometer.
- Introduce a spectrometer and show the parts like prism table, telescope and collimator. Now place the prism in the prism table and level it so that seven distinct colors are visible through the telescope. Let each student to watch the spectrum through the telescope.
- Now place another prism near the first one in such a way that their refracting angles are in opposite direction so that, the dispersion produced by one prism is nullified by the other and white light is visible through the telescope.
Activity for Light Lesson Plans
Cardboard sheet
Color paper or color pens
Gum
Scissors
Pencil
Battery powered fan
Eraser
click to enlarge
Procedure
- Take the two prints of the image shown. Divide students into two groups and as directed in the image, either color each portion with respective colors, or use color papers. In this image the violet section is more prominent, instead allow one group of students to make a disco with more violet and another with more red portion. Paste the paper in the cardboard sheet and remove the remaining portion.
- Make a hole in the middle of the cardboard sheet and insert a pencil through the hole. Make a hole in the eraser so that the pencil pass through it.
- Now fix the eraser in front of the disco so that the disco won’t be detached from the pencil when students rotate it fast. Teachers can rotate it with hand but it must be done very fast otherwise, the desired result will not be obtained. So it is better to use battery powered fan. Remove the blades of the fan and then fix the disco on the pointed end in the center of the fan and switch it on. As the fan rotates the disco, students can observe the white light.
Analysis and conclusion:
From the observation of these activities students will understand that visible light is not monochromatic but it is a combination of seven colors and they are Violet, Indigo, Blue, Green, Yellow, Orange and Red.
