Planck's Constant Lab

Purpose
                   The purpose of this lab is to be able to determine the value of the Planck's constant experimentally. This could be done by measuring the energy of different colors of LED and determine the wavelength for each. In this lab, the blue and yellow LED are used to determine the Planck's Constant.

Experimental
Simple circuit is built as follow and the voltage is measured

Spectrum of Blue LED

Based on the experiment ,the data obtained is as follow:

Color	Wavelength	Energy
Blue	450 nm	1.95 eV
Yellow	590 nm	2.76 eV

From the equation E = hc/lambda

We can find the relation of lambda being lambda = hc/E

Which also mean that hc is our slope of the graph.

Since c is constant being 3*10^8 m/s , we can find h

h = m / c = 1*10^-25 / 3*10^8 = 3.33*10^-34

The theoretical value for Planck's Constant is 6.628 *10^-34 which mean our percent error is 50%.

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.

Activphysics Activities

Introduction

             The purpose of this activities is to understand the theory of relativity of time and length. In this activities, some of the relativity theories will be simulated in the activities.

Activities

Questions on Relativity of Time

1. The distance of the stationary light clock is shorter than that of the moving clock as shown in picture above.
2. The time of the moving clock is greater relative to a stationary frame of reference than the stationary clock.
3. In the moving frame of reference, the time interval of the light of the moving clock is the same as the stationary clock
4. As the velocity of light clock decreased, the time interval difference will also decrease.
5. delta_t = 1.2 * 6.67 µs = 8.00µs
6. gamma = 7.45 / 6.67 = 1.12

Questions on Relativity of Time

1. The round trip is independent of the velocity
2. The round trip time interval will be longer observed from earth since there will be a value for gamma.
3. It can't be equal since by saying it is equal, it means there is no time dilation.
4. L = 1000 / 1.3 = 769m

Lenses

Purpose
            The purpose of this lab is to be able to analyze the characteristic of a converging lens to the image. In this experiment, a lens with measured focal length will be set in front of a light source and the image obtained from the light source. In this experiment, the distance from lens to light source and the lens from the image is measured. The image is measured when focus is achieved.

Experimental
   
The setup for the lab is as follow

Setup of the lab

different angle of the setup

The shape of the image

Measurement of the image distance

Light source for part 2 using different object

The image of the object used

Data and Analysis

Focal Length = 20cm ± 0.5cm

Object distance (cm)	Image distance (cm)	Object height (cm)	Image Height (cm)	M	Image Type
100	23	5.1	1.7	0.333	Inverted, real
80	24.5	5.1	2	0.392	Inverted, real
60	28	5.1	2.5	0.490	Inverted, real

Conclusion
                Based on the result obtained, the object and image distance is indeed have an inverse relationship as shown in the first graph. On the second graph, we shows that it has linear relationship between the inverse image versus the negative inverse object distance. Since we didn't have the time to complete the actual lab, the image of the 0.5 focal length distance is unknown, but we predicted for it to have inverted, real image but it will be rather difficult to focus the image in the board. Some error that contributes to the accuracy of the graph is the lenses used might have deteriorated a little bit which change the focal length for a little bit.

CD Diffraction

Introduction
          In this experiment, the distance between the grooves of a compact disc will be determined. One of the method to measure it which we are using in this lab is to use the diffraction of the disc. In this experiment, a laser will be used to shine a CD and the diffraction pattern is then measured and the distance of the grooves will then be able to be calculated.

Experimental


First the lab is set up as follow:

Setup of the lab

Measurement that is made in the experiment

The data from the measurement is tabulated below:

Distance from disc to board (cm)	45.2 ± 0.05
Distance of diffraction pattern (cm)	21.25 ± 1.25
Wavelength of laser (nm)	633 ± 1 nm

The data obtained is as calculated to be d = 1485 ± 20 nm

The theoretical distance of the grooves are 1600 nm

From these data, the percent error is calculated to be 7.19%

Conclusion

              

                Based on the data obtained, the distance between the grooves appear to be 1485 ± 20 nm with a percent error of 7.19%. Some of the error that contributes to the percent error is that there is couple of scratches and smudges. Although the percent error is quite high, it is still accurate as the true value is still within uncertainty.