To draw the path of a ray passing through a glass slab and, hence, to measure the angle of incidence and the angle of image.
AIM : To draw the path of a ray passing through a glass slab and, hence, to measure the angle of incidence and the angle of image.
PRINCIPLE : When an oblique ray of light enters from one transparent medium to another transparent medium, at the surface separating these two media, the light ray changes its path. This phenomenon is called refraction of light. When a ray of light passes through a glass-slab, it is refracted twice, as a result of which, the emergent ray becomes parallel to the incident ray.
APPARATUS : Glass –slab, Drawing-board, Drawing paper (White), Foot-rule, Pencil, Pins, Push pins and Protractor.
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| Paper fit with pins and set Glass Slab |
Ø Fix a white drawing-paper on the drawing board using push pins. Now place the glass-slab on it and mark its position PQRS by drawing its out-line using a pencil.
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| Draw Ray AB not perpendicular to PQ |
Ø Now draw a ray AB such that it is not perpendicular to PQ. Fix two pins upright with separation of 2-3 cm on this ray.
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| See Image from another side and set P3 P4 |
Ø Now try to see the images of P1 and P2 from side RS and fix pins P3 and P4 upright so that images of P1 and P2 and pins P3 and P4 become collinear at their lower ends.
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| Remove pins and Glass slab |
Ø Now remove the slab and the pins obtain emergent ray CD by drawing a line passing through marks of P3 and P4, which intersects RS at C.
Ø Join B and C to complete the path of the ray. Now draw a normal MN to the surface PQ in such a way that it passes through B. Also draw M’N’, through C to the surface RS.
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| Measure Angle of Incidence and Angle of Emergence. |
Ø Measure ÐAMB (Angle of Incidence) and ÐOCN’ (Angle of Emergence).
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| By changing Angle of Incidence repeat the experiment |
Ø Repeat the experiment for various values of angle of incidence AMB and note your observations in the table.
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