Properties of Lens and Mirror Using Parallel Beam
To know the physics of the light box developed at Anveshika.
Light box is a special equipment designed by Anveshika. It has three slits. The light box contains a 12 V bulb. The power to the bulb is provided by a 220 V to 12 V step down transformer. The light from the bulb passes through a lens and comes out as three parallel beams from the slits. We can close a slits by putting a black tape on it.
Light box, mirrors and lenses of different types.
- Carefully open the light box. See the light bulb, lens, and three slits.
- Now, adjust the bulb (by moving cylindrical rod) so that you get a parallel beam of light. Where is the bulb located with respect to the lens? What is approximate focal length of the lens?
- How do you know that beam is parallel? For the beams to be parallel, the distance between the beams should not change with change in distance from the source.
- Now, see the effect of convex lens, concave lens, concave mirror and convex mirror on the parallel beam.
The bulb is like a point source of light. We get parallel beam of light when bulb is placed at the focus of a convex lens.