physics investigatory project

PHYSICS INVESTIGATORY PROJECT NILANJANA MISHRA CLASS-XI-SC ROLL NO.-15 2014-2015 KENDRIYA VIDYALAYA IIM JOKA

ACKNOWLEDGEMENT

I deeply acknowledge my sincere thanks to my physics teacher Miss Soumi Banerjee

for her guidance and advices to complete my project successfully as well as for providing me all the facilities to finish the project on stipulated time.

CERTIFICATE

NAME : NILANJANA MISHRA science

CLASS : XI

ROLL NO. : 15 INSTITUTION: KENDRIYA VIDYALAYA IIMC JOKA

This is certified to be the bonafide work of the student in the PHYSICS INVESTIGATORY PROJECT during the year 2014-2015 .

Certified by:…………………………… …….

Miss. Soumi Banerjee

        

CONTENT

ACKNOWLEDGEMENT CERTIFICATE THEORY AIM APPARATUS PROCEDURE OBSERVATION RESULT BIBLIOGRAPHY

THEORY When light passes from one medium into an optically different medium at an angle other than normal to the surface, it is "bent" or undergoes a change in direction, media. This bending, or change in the direction of the ray occurs only at the interface between the two materials. The interaction of the light with the transparent material changes the speed of light as it passes through the material. The relationship between the speed of light in a vacuum c and the speed of light in the material v is known as the index of refraction n.The index of refraction is defined in the following equation:

n = c/v

(1)

Where c is the speed of the light in vacuum and v is the speed of the light in medium. Equation (1) can be used to find a relationship between the angle of the incident wave, still measured with respect to the normal, and the angle of the light ray as it moves through this second material, known as the angle of refraction. This new relationship is known as Snell's Law, stated mathematically in the following equation:

n1 sin(i)= n2 sin(r)

(2)

Where (i) is the angle of incident, (r) is the angle of refraction, n1 and n2 are the indices of refraction of the first and the second medium, respectively. If the incident medium is air n1 = 1, then

sin (i) = n2 sin (r) n2= sin (i)/ sin (r)

(3) (4)

AIM:Verification of Laws of Refraction of Light and Determination of Refractive Index of the Glass.

APPARATUS :     

A rectangular slab of glass, a laser pointer a few sheets of paper a sharp pencil a ruler A Protector

Procedure  Place a flat sheet of paper on a flat surface.  Place or mount the laser pointer such that its ray is not only horizontal to the sheet of paper, but also travels very close to its surface and leaves a streak (line) of red light on the paper. Some adjustment and practice is crucial.  When an uninterrupted streak of light is present, place the rectangular or square slab of glass on the flat paper such that the laser ray is incident on a clear side it (as shown in the figure) and exits from the opposite side. With a sharp pencil, draw four straight lines around the slab in order to register the location of the slab on the paper.  The ray incident on side AA of the slab making angle i1 with NN does refract and enters the slab through angle r1. See Fig. In glass, it travels to the opposite side BB and becomes incident on the other side through angle i2 and finally refracts back into air through angle r2. Mark two points on the incoming ray and two dots on the outgoing ray (with the sharpened pencil) in order to register their locations. Make sure to mark points 1 and 2 (points of incidence) as well.

 Lift the slab and turn the laser off. On the paper, connect the marked points in order to reproduce the laser ray trace.  Draw two NN (Normal) lines as seen in the figure at points marked 1 and 2. Measure angles i1, r1, i2, and r2 by a protractor.  Use i1 and r1 and the Snell’s formula to find n, the refraction index of the glass slab. Use i2 and r2 to find n again. Find the average of the two values you find for n. Use this average as your measured value for n.  Determine the index of refraction through your observation