To observe refraction and lateral; deviation of a beam of light incident obliquely on a glass slab.

Observing the refraction and lateral deviation of a beam of light incident obliquely on a glass slab is a classic physics experiment that helps demonstrate the principles of refraction and how light changes its path when it crosses from one medium to another. Here's how you can set up and perform this experiment:

Materials you'll need:

Glass slab (rectangular or triangular in shape)
A light source (a laser pointer, flashlight, or a ray box with a slit)
Protractor
White paper or a plain wall to project the light onto
Ruler
Pencil
Transparent adhesive tape
Dark room or a dimly lit area
Procedure:

Set up your experiment in a dark room or a dimly lit area to make it easier to see the path of the light.

Place the glass slab on a flat surface. Ensure it's clean and free of any dust or fingerprints.

Position the light source so that it shines a narrow, well-defined beam of light onto the glass slab. If you're using a laser pointer, shine it directly at one of the longer sides of the slab. If you're using a ray box, place it in such a way that the light passes through the slit and hits the glass slab.

Use a protractor to measure the angle of incidence. This angle is the angle between the incident ray (the incoming light) and the normal to the surface of the glass slab. The normal is an imaginary line perpendicular to the surface of the slab at the point where the light enters it.

Place a sheet of white paper or a plain wall behind the glass slab so that the light beam is projected onto it. You should be able to see the path of the light on the paper or wall.

Carefully trace the path of the incident ray (the incoming light) and the path of the refracted ray (the light that passes through the glass slab). You can use a ruler and a pencil to do this.

Measure the angle of refraction. This angle is the angle between the refracted ray and the normal inside the glass slab.

Measure the lateral deviation. Lateral deviation is the horizontal distance between the incident and refracted rays where they intersect the paper or wall. Use a ruler to measure this distance.

Record your observations, including the angles of incidence and refraction, and the lateral deviation.

Repeat the experiment with different angles of incidence by changing the angle at which the light strikes the glass slab.

Analysis:

As you change the angle of incidence, you should notice that the angle of refraction also changes, and the lateral deviation varies accordingly. This experiment demonstrates the principles of refraction and how the speed of light changes as it passes from air into the glass, causing it to change direction.

You can further analyze your data to calculate the refractive index of the glass slab using Snell's Law, which relates the angles of incidence and refraction to the refractive indices of the two media (air and glass).