[PDF] Diffraction and Compact Discs - SMU



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Introduction

This is an adaptation of a practical I saw on Youtube where a CD is used to perform a diffraction experiment, so thanks go to Steve Dickie. The information on a CD is stored on a very thin shiny spiral track. When light shines on these thin lines it is diffracted in all directions, the light from neighbouring lines interferes constructively when th...

Theory

The CD is acting as a reflecting diffraction grating. Each line is very thin and diffracts light at all angles as seen in the diagram on the right. When brought to a focus in the eye parallel rays of light from each line interferes with light from the other lines. Constructive interference happens when the path difference is one whole wavelength so...

How does diffraction in a CD work?

  • visible light - How does diffraction in a CD work? - Physics Stack Exchange Closed 1 year ago. From my shallow understanding of diffraction, my notes say that a CD acts as a diffraction grating that produces rainbow colors. In Young’s double slit experiment, we see the fringes on a screen.

What is the Order of diffraction?

  • where b is the distance between two adjacent slits, called a grating constant or a grating period, and k = 0, 1, 2, … is the order of diffraction. A recording on a CD is in the form of microscopic pits of different lengths that carry the information.

What is diffraction of light?

  • Diffraction (bending) of light is due to wave properties of light. It means that when a light wave encounters an obstacle, it does not propagate linearly behind the obstacle.

How does a diffraction grating work?

  • The CD is acting as a reflecting diffraction grating. Each line is very thin and diffracts light at all angles as seen in the diagram on the right. When brought to a focus in the eye parallel rays of light from each line interferes with light from the other lines.
Describe the concepts of diffraction and interference in CDs or DVDs. Ans: In CDs or DVDs, the discs themselves act as the diffraction gradient for the laser beam. As the laser beam is focused directly on the CD or DVD the laser beam is reflected. When it is reflected interference occurs, the waves overlap and diffraction patterns become visible.