Angle of deviation of GLASS PRISM, GBSE practical for std 11 & 12.

Angle of Deviation of Glass Prism

ANGLE OF DEVIATION OF GLASS PRISM, 

12.1  AIM :-

Determine with the help of pins, the angle of the given glass prism. Determine the values of angle of emergence and angle of deviation for four different values of angle of incidence. Hence prove that  i + e = A +d.

PRINCIPLE : Reflection and refraction of light.

APPARATUS:  Glass Prism, Drawing paper, Drawing board, Pencil, Ruler, Pin, Protector,

PRECAUTIONS

Ø    While marking the position of a prism with pencil, the prism should not be disturbed.

Ø   A prism should be carefully put back exactly at the marked position.

Ø    While pressing the heads of the pins for fixing them use metal coin or a hard object so that you do not hurt your palm.

Ø    Do not press the pins very hard in the board otherwise it becomes difficult to remove them afterwards.

Ø   See that the pins pushed in the board remain perpendicular to the board.

PROCEDURE :

Take paper and pin it on Drawing board. 

Now take Glass prism and put it on center of Drawing board paper.

Mark the edges of the prism with pencil.

Angle of Deviation of Glass Prism Practical

Draw line P₁ M perpendicular  to prism base BC.

Insert two pins vertically P₁ & P_2..

Place the Prism on its original position.

NOTE :- Pins should be 3 – 4 cm. away from each other.

Observe pins from the side AB and insert two pins P’₁ & P’₂ such that images of P₁ ,P₂ and pins P’₁ & P’₂ are collinear.

Angle of Deviation of Glass Prism Procedure

Draw line Q₁ N perpendicular  to prism base BC

Insert two pins verticallyQ₁ & Q_2.

Angle of Deviation of Glass Prism Procedure

Place the prism on its original position

Observe pins from the side AC and insert two pins Q’₁ & Q’₂ such that images of Q₁ ,Q₂ and pins Q’₁ & Q’₂ are collinear.

Angle of Deviation of Glass Prism Procedure

Measure angle with protector ÐP’₁OQ’_1.

Angle of PRISM = ÐP’₁OQ’₁  / 2.

Angle of Deviation of Glass Prism Procedure

For more details view Video

Angle of Prism:

REFRACTIVE INDEX OF GLASS PRISM measure with Glass Prism for std 11 & 12 GBSE

Refractive index of  Glass Prism

REFRACTIVE INDEX OF GLASS PRISM 

12.2  AIM :-

Using pins with a given prism determine the angles of deviation for six different values of angle of incidence. Draw the graph of angle of deviation versus angle of incidence. Determine, from this the angle of minimum deviation and using following formula determine refractive index of material of the prism.

Formula for Refractive index of Glass Prism

Angle of prism, A = ……. .

APPARATUS:  Glass Prism, Drawing paper, Drawing board, Pencil, Ruler, Pin, Protector,

FORMULA : - A + d = i + e

PROCEDURE :-

Take paper and pin it on Drawing board. 

Now take Glass prism and put it on center of Drawing board paper.

Mark the edges of the prism with pencil

Refractive index of  Glass Prism procedure

Draw N₁Q perpendicular to AB

Draw a line PQ making an angle i of 35^O with N₁Q

NOTE :- Pins should be 3 – 4 cm. away from each other.

Fix two pins vertically on line PQ  at point L & M.

Refractive index of  Glass Prism procedure

Place the prism in its original position.

Refraction takes place QR after placing prism on its original place

Now look from surface AC, adjust pin N & O vertically on the side which you are looking so that the images of the pins L & M and the pin N & O appear to be in the same straight line.

Refractive index of  Glass Prism procedure

Draw a line  SR

Measure d = Ð UDN

Refractive index of  Glass Prism procedure

Draw a line SR, and draw a perpendicular N₂R at R to the line AC

Measure  e (Angle of Deviation)

Refractive index of  Glass Prism procedure

Refractive index of  Glass Prism procedure

Note :- Repeat the experiment by taking different angles of incidence viz.,

 40 ⁰, 45 ⁰, 50 ⁰, 55 ⁰ and 60 ⁰.

For more details View Video

Angle of Deviation.

Draw the path of through glass slab and, hence, to measure the angle of incidence and the angle of image.science practical std 8 to 10

Rays passing through Glass slab

Rays passing through Glass slab

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.

PROCEDURE :-

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.

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.

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.

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.

Ø  Measure ÐAMB (Angle of Incidence) and ÐOCN’ (Angle of Emergence).

Ø  Repeat the experiment for various values of angle of incidence AMB and note your observations in the table.

Glass Slab for Practical

Rays passing through Glass slab

Rays passing through Glass slab

Rays passing through Glass slab

Rays passing through Glass slab Observation table

CONCLUSION :

PRACTICAL USES :

We can study  the path of a ray when it passes through a glass slab. Here emergent ray and incident ray are parallel, but there is some distance between them. This distance depends on angle of incidence, breadth of the slab, and type of material used in the slab. i.e. refractive index of the material. From these information we can have an idea of the refractive index of the material used.

For more details view Video.

Rays passing through Glass slab.

Determine focal length of Convex lens of a far distance object std 8 to 12 GBSE.

Focal length of Convex lens

To determine the focal length of a convex lens by obtaining an image of a far distance object. 

AIM  : To determine the focal length of a convex lens by obtaining an  image of a far distance object.

PRINCIPLE   :  Rays parallel to the axis, after being refracted by a convex lens, are focused on the principal focus. Distance between the optical centre and the principal focus is known as the focal length.

APPARATUS   :   Convex lens, Stand, Screen, Foot-rule, Paper, Pencil,

Convex lens to find Focal lens

Observation

Conclusion

Practical uses

Convex lens of proper focal length are usedin optical instruments like simple microscope, compound microscope, telescope, etc,. Also the method given here in the simplest way to estimate the focal length of a convex lens.