Diffracting grating is a device that has an array of many parallel slits. It is used by most Researchers to measure the wavelength of light accurately since it is difficult to do that with either the single-slit or double-slit. It is a tool of choice for separating light of different wavelengths with high resolution, then a diffraction grating is most often the tool of choice.
Teacher review the last week’s lesson on Single-slit diffraction by asking probing questions.

Teacher discusses diffraction grating and how Gratings are used as a Spectrometer with students 

Students use CD and DVD as diffracting grating and determine the groove spacing of each using telescope and a bright light source. Students are to use their data to assess which disc can hold more data and explain why.
Watch Youtube video on Diffraction Grating.

 Fig: Image of seperation using diffraction grating

FIG: CD SOURCE: http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/grating.html

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