Young's experiment and the dual nature of lightFeatured science projectScience project video

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Complexity level:
9
Project cost ($):
20
Time required:
It will take an hour to set up the experiment, and an hour to conduct it
Material availability:
The materials required for this science experiment can be purchased at a department store.
Safety concerns:

Basic safety requirements.

Abstract

Light has a dual nature: it has the characteristics of both waveforms and particles. This science project was conducted in order to help us better understand the dual nature of light. This paper explains the double split experiment which is also known as Young's experiment, and how the experiment demonstrates the waveform nature of light.

Hypothesis

The double slit experiment will prove that light has the properties of waveforms.

Background

Dual nature of light

Light has the ability to demonstrate the behavior of both particles and waveform. The double split experiment, also known as Young’s experiment, demonstrates the wave-like behavior of light: where interference of light causes the formation of light and dark lines on a screen. Also, the particle properties of light can be demonstrated through photons. This wave-particle dual nature of light is studied under the field of quantum mechanics.

The waveform behavior of light enables us to understand the different colors of light around us. Electromagnetic rays from the sun consist of waveforms that have different frequencies and wavelengths. Each band of frequency in the visible light spectrum is seen as a different color.

Light is also known to exist as photon particles. These particles do not have a mass, are without electric charge and do not decay. Photons are carriers of electromagnetic force and are able to demonstrate the properties of both waves and particles.

Scientific Terms

Particles, waveform, Young's experiment, interference, quantum mechanics, electromagnetic, photon

Materials

The materials required for our project are as follows:
- a light source (for example, a laser pointer)
- 2 sheets of cardboards 100mm x 100mm in size
- a paper cutter
- a stack of newspapers
- a white board to act as the screen

Procedure

1. Two small slits are made in the middle of the first sheet of cardboard. The cardboard sheets are placed on the newspaper stack before they are cut. This will prevent the table from being damaged. The slit should be 1 mm x 5 mm. The slits are parallel to each other and 5mm apart. Only one slit about 1 mm x 5 mm is made in the middle of the second sheet of cardboard.

 double slit experiment

2. The experiment is set up as illustrated in figure 1. The light source is placed in front of the cardboard sheet and the whiteboard acting as the screen is placed at the back.

3. The distance between the light source and the screen is adjusted so that the diameter of the circle of light that falls on the slits is larger than the slits on the cardboard. The experiment is best performed in a dark room with the lights switched off.

4. The tests are done using the cardboards with 1 slit and 2 slits. The light patterns on the white board are observed. The distance between the white board, the cardboard and the light source are to be adjusted to obtain the best results.

Observation

The results seen on the white board screen are shown in figure 2. When light passed through the cardboard with only one slit, it was diffracted. A narrow band of light, which is bright in the center and dim at the sides, was observed.

young's slit experiment science project

When the test was repeated using the cardboard sheet with 2 slits, light leaving both the holes were diffracted. The diffracted light from the 2 slits met and "interfered", resulting in the interference pattern of dark and light bands on the whiteboard screen. The pattern on the screen also widened by 3 to 4 times.

Conclusion

The double slit experiment proves the wave properties of light.

Also consider

Vary the size of the slits. Do the patterns on the screen change?

Put pin holes into the cardboards. Make holes in different locations. How do the patterns on the screen change?

References

Double slit experiment - http://en.wikipedia.org/wiki/Double-slit_experiment

Photon - http://en.wikipedia.org/wiki/Photon

Wave-particle duality - http://en.wikipedia.org/wiki/Wave%E2%80%93particle_duality

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