Trisha Banerjee @ 2010

Whole setup of the experiment:-

Light source

Illuminated slit wit cross wires

Nodal slide

Vertical plane mirror

Trisha Banerjee @ 2010

Directions of rays:-

Trisha Banerjee @ 2010

Lens keeping stand

Position of the lens on slide

Screw to move the stand

Apparatus :- Nodal slide assembly and two convex lens.

Procedure in brief:-

The nodal slide is clamped in front of a screen with an illuminated slit fitted with cross wires .on the other sides remote from the screen, is mounted a vertical plane mirror. The distance between the screen and the lens system is adjusted in such a way that a well defined image of the slit is obtained on the screen adjusted to it.

obviously the , centre of the slit is at the first principal focus of the system. The carriage is now rotated through a small angle and it will be found that the image shifts sideward's to the right or the left. The carriage and the upright ( stand) carrying the nodal slide are then adjusted such that the direction of rotation of the image changes its sign and finally the image remains stationary for a slight rotation of the carriage.

The distance between the screen and the axis of the rotation for no shift in the image measures the first principal focal length of the lens system. The other focal length can be determined by the turning the nodal slide through 180 degree and repeating the experiment.

Trisha Banerjee @ 2010

Screw to move the carriage longitudinally

Trisha Banerjee @ 2010

Nodal slide:-

Setting of the nodal slide:-

To locate the Nodal points , the lens system is mounted with its axis horizontal on a carriage which can be rotated about the vertical axis and can be moved longitudinally with the help of a rack and pinion arrangement . This apparatus is known as Nodal slide.

Note:-

parallax should be removed very carefully and the stationary points also.

Trisha Banerjee @ 2010