Module 5

Module 5—Wave Theory of Light

 

Reflect and Connect

 

Why does a diffraction grating, such as on a CD or DVD, produce a full spectrum rainbow when white light is incident on the grooves making up the track? In both simulations used in this lesson, you can vary the colour (wavelength) of light and you will notice that the interference pattern shifts location. In other words, the dark and light bands of green light appear at different locations than the dark and light bands of red or blue light.

 

This occurs because the amount of diffraction depends on the wavelength of light when all other variables are held constant. Longer wavelengths diffract through larger angles. When white light is incident on a diffraction grating, each colour diffracts to varying degrees according to its wavelength, effectively separating the colours. This makes each bright fringe appear as a mini-rainbow in a larger interference pattern of bright and dark fringes similar to the patterns observed when monochromatic (single colour) light is used.

 

The processes of polarization, diffraction, and interference, as observed in double-slit interference experiments like Thomas Young’s, provide strong evidence that light and EMR in general exhibit wave-like characteristics.

 

Module 5: Lesson 6 Assignment

 

Remember to submit the Module 5: Lesson 6 Assignment to your teacher.

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