CBSE Class 12 Physics Activity 5 notes offer a comprehensive guide to mastering the practical experiment. These notes include detailed explanations, step-by-step procedures, and essential tips to help students understand the underlying concepts, ensuring they can successfully perform and analyze the experiment with confidence.
CBSE Class 12 Physics Activity 5
Aim
To observe diffraction of light due to a thin slit.
Materials Required
Two ordinary razor blades with sharp edges, a source of light i.e. a pencil laser or a sodium lamp, screen, and black paper.
Theory
When a beam of monochromatic light falls on a narrow slit of small width, the light bends around the edges of the slit. If a screen is placed at a suitable distance, a diffraction pattern due to the slit is obtained.
“The phenomenon of bending of light around corners and spreading into the regions of geometrical shadow is called diffraction”.
The diffraction pattern consists of a central maxima surrounded on either side by several alternate dark or bright bands called secondary minima and maxima.
Diagram
Procedure
- First of all, I placed two sharp-edged, razor blades side by side on a strip of black paper keeping their sharp edges close and parallel to each other as shown in the figure, then I fixed the blades with the help of cello tape and made a fine slit.
- Switched on the sodium lamp or pencil laser and kept it at approximately 2 meters from the blades.
- Let the light coming out of the slit fall on a screen(or wall) situated at a distance of about 20 cm.
- A diffraction pattern consisting of dark and bright bands was observed on the wall. If an ordinary lamp is used in place of a sodium lamp, coloured fringes will be observed.
- Repeated the experiment by increasing the slit width.
Precautions
- The source of light should be kept at least at a distance of 2 m from the thin slit between the two blades.
- The edges of the two blades should be held parallel and close to each other.
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