lap report Absorption and emission experiment
Zozo moon
report4.docxIntroduction
In this experiment, a Michelson interferometer is built and examined how certain characteristics of light sources/waves can be measured using it. As the name suggests, Interferometer is works based on the principle of the merger of two or more light sources to create interference. The interferometer can be used to measure the wavelength of a light source, to calculate the refractive index of a material, to measure the coefficient of thermal expansion of a material, to study the white light interference and to study how the interference pattern is affected by the coherence length of the source. When determining the wavelength of the light source () using the following formula, the light transitions occurred as the mirror is moved, shall be counted.
Where, x = distance that the mirror moved
N = no. of transitions.
To study the concept of coherence length which is defined as the maximum length between the ferrometer arms that permits the interference to have occurred, the position of the mirror shall be adjusted until the interference pattern is close to disappearing. To calculate the coherence length(Lc), the following formula is used.
Where, 0 = coherence length
= bandwidth
To calculate the refractive index of a material, a Plexiglas plate is placed and is rotated to change the optical path length to create light transitions. The following equation is used to calculate the refractive index (n) using the measured values;
Where, N = no.of transitions
= wavelength of the light
t = thickness of the Plexiglas plate
= rotation angle of the plate
To calculate the coefficient of thermal expansion (α ) of an aluminum rod, the rod is heated while measuring the temperature and counting the light transitions occur due to the shift of the mirror.
Where, N = no.of transitions
= wavelength of the light
L0 = original length of the rod
T = Temperature change
https://www.ligo.caltech.edu/page/what-is-interferometer
https://en.m.wikipedia.org/wiki/Michelson_interferometer
