This practical is to verify the law of refraction of light. We have read about the refraction of light in oscillabers and there are some laws of refraction of light. We can verify these laws by performing an experiment in the laboratory. In this practical we are going to verify some laws of refraction of light. We need the following apparatus. Stectangular Glass Slap Soft drawing board drawing pins Paper pins drawing sheet. We fix the paper on drawing board properly using drawing pins. We place the glass slab on this paper at the center and we draw the boundaries of the slab on the paper with a pencil. PQRS The pencil has to be sharp for the accuracy. Take a point O on the boundary line PQ of the slab. Draw a normal at point O. Normal is perpendicular. So we draw perpendicular M1 and 1 at point O. The angle M1 OP is 90 degree. Then we draw a ray passing through O and making an angle of 30 degree. Let us call it as AOM1. This ray is called incident ray and the angle is angle of incidence. So we are doing this experiment with the angle of incidence 30 degree. Remember that 30 degree is the angle between AO and M1O. Then we place the glass slab in such a way that it matches PQRS. We place two paper pins 1 and 2 on the ray AO. Look through the slab from other side. SR We can see the pins 1 and 2 through glass slab. They are linear. Now we fix a third pin on the side of SR in such a way that this pin 1 and 2 appear to be collinear. We take fourth paper pin and place it in such a way that it is in the same line as the other three pins. Remove the glass slab. Join this pin 3 and 4. Extend this line up to SR. We will get point of intersection between SR and this ray called emergent ray. Let us call this emergent ray BC, where B is the point of intersection between SR and the emergent ray. We draw normal or perpendicular to SR at point B and name it M2N2. The angle between BC and M2N2 is called angle of emergence. We have to measure this angle also and write it down. Join point O and B. Ray OB is actual path of ray through glass slab. Now we have light ray passing through glass slab in such that its path is indicated by A OBC. We have extended ray A O in the glass slab with dotted lines as if there were no glass slab. Let us call it ray OD, AD and BC. Are parallel to each other. The angle N1OB is angle of refraction and is denoted R. We have three angles with us, angle of incidence, angle of refraction and angle of emergence. Repeat the experiment using angles 45 degree and 60 degree instead of angle 30 degree. Fill in the observation table in which you are supposed to write angle of incidence, angle of refraction and angle of emergence. That is I R and E. Our conclusion is that light undergoes refraction when it enters from air to glass and again when it enters from glass to air. When light undergoes refraction through glass slab, the incident ray and immigrant ray are parallel to each other. We can check by measuring perpendicular distance between these two rays. Killing the angle of incidence and the angle of emergence are of same measure. Angle of refraction is smaller than angle of incidence. These conclusions verify some laws of refraction.