Light and Matter Waves (VPhyton)

Activphysics: Laser

Introduction


The purpose of this activity is to understand the concept of how laser is built. We will explore the absorption process, spontaneous emission and stimulated emission. When all three are combined together, laser will be emitted.

Absorption

Spontaneous Emission

Stimulated Emission

Laser  

Conclusion

                 In the absorption, we can see that the difference of Nin and Nout gives us the value of photon absorbed. In the spontaneous emission, we can see that the photon is emitted in random direction. When the excited photon is stimulated further by a light, it will emit photon in the direction of the light that stimulates it. This phenomena is called the stimulated emission.We figure out that the pumping level required for population inversion is 65.

Color and Spectra

Introduction
               The purpose of this lab is to view the spectrum of colors found in white light and observe the effect colored filters have on the spectrum of white light. We will also measure the wavelength of a hydrogen gas lamp and an unknown gas and be able to predict exactly the type of gas it is. When a light shone through the diffraction grating, the light will be scattered and the distance of the scattered light to the light source will be measured since wavelength can be calculated using the following relationship

Derivation of the formula to find wavelength

 Experimental
 In the first part of the experiment, we set up the equipment and use the white light source as such

setup of equipment for the one with white light source

Result observed through diffraction grating

Data collected and equation for the callibration

In the second part of the experiment, we try to determine the unknown gas again by using the diffraction grating and the same setup as before:

The setup with unknown gas that has bright blue color

Result observed through diffraction grating

Data obtained for the experiment

The result shows that the unknown that we have is of mercury gas as shown below by the color and the spectra of mercury found in a website

spectra for mercury gas

 As shown from the data above, the wavelength observed approximately coincide with the spectra of the mercury gas. The light that it emits also look somewhat the same as the color above.

In the next part of the experiment, hydrogen gas is observed

The color of hydrogen gas

Data obtained from the observation of the hydrogen gas

Conclusion
              In the first part of the experiment, the data for the white light source is taken. It is then matched with the actual wavelength of each color giving the relation ship shown as lambda_prime above. This is used as a calibration for the second and the third part of the experiment, which is to measure the wavelength of an unknown gas and the hydrogen gas. The wavelength of hydrogen gas and the mercury gas is indeed under the uncertainty which makes the value quite accurate. One problem that we encounter is that instead of having 4 different light spectra in the hydrogen gas, we can only observed three. The green light does not show up when we observed it. One of the explanation that we can give is that there is some impurity in the hydrogen gas which makes the green light spectra disappear such as the hydrogen gas has been mixed with air. The unknown gas that we have, the unknown gas #1, appear to be mercury according to the visible light spectra and the wavelength of the light emitted as shown on the data above.