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.

focal length of a concave mirror by obtaining an image of a far distance object, GBSE for std 8 to 10 science practical

Focal length of a concave mirror

     

Focal length

To determine the focal length of a concave mirror by obtaining an image of a far distance object

AIM :- To determine the focal length of a concave mirror by obtaining an image of a far distance object.

APPARATUS  :- A concave  mirror of diameter approximately 10 cm., stand, screen, foot-rule, etc.

PRINCIPLE   :- Rays coming from a far distance object are almost parallel. Such rays, parallel to the principal axis, after being reflected by a concave mirror, are focused at the principal focus of the mirror. Distance between the principal focus and the pole of the mirror is known as the focal length.

NOTE  :  Here screen should be taken small, so that rays coming from the object are not blocked by the screen itself. Diameter of the screen here can be    approximately 3 – 4 cm.

Focal length of Concave mirror

Focal length of Concave mirror,

Focal length of concave mirror Adjustment

Focal Length of Concave mirror

OBSERVATION

Distance between the pole of the mirror and the image on the 

screen = focal-length =                              CM.

CONCLUSION

PRACTICAL USES

Concave mirrors are used in head lights of vehicles, solar furnace, solar cooker, shaving mrror, etc. For all such applcatons it is necessary to know the focal length of the mirror to used. It can be estimated using the given method.

For more details view Video.

Focal length