-: MAKING A KALEIDOSCOPE :-

It is an optical instrument that forms beautiful patterns, It contains two mirrors which meet at an angle of 600. Light from coloured objects placed near the mirrors-bounces between them to form several reflections. The most fascinating aspect about the kaleidoscope is that you never get the same pattern twice. Designers of wall papers and fabrics make use of this instrument to get ideas for new patterns.

*** MATERIALS REQUIRED ***

• Take two rectangular strips of mirrors identical in size about 8 inches long and 2 inches wide. Take one cardboard piece of the same size as the mirror strips. Join the mirrors and the cardboard together to form a long triangular tube. The slivered sides of the mirrors should face inward. The angles between them will be 600. This angle will produce six symmetrical patterns.

• Cut a piece of tracing paper or plastic paper to fit over one end of the triangular tube and glue or tape It in place. 

• Take about 7-8 pieces of bangles of different colours. Put these coloured pieces In the tube. Then hold the tube upright so that the pieces rest on the tracing paper. 

•  Look down into the tube and see the pattern formed. The end of the triangular tube near the eye can be closed by a transparent plastic sheet or glass sheet. The pattern will consist of 6 IdentIcal sections. Shake the kaleidoscope to change the patterns.

 

-: MAKING A SLIDE PROJECTOR :-

A slide projector is an optical instrument used to see slides on a screen in an enlarged image. It makes use of a good quality magnifier and a light source. When light falls on the slide, its enlarged image is projected on a screen. This simple project will demonstrate the principle of projection. 

-: MATERIALS REQUIRED :-

• Take one magnifying lens of about 3 inch diameter and 50 cm focal length.
• Take one cardboard box with a deep lid and of the same height as that of the focal length of the lens. The other dimensions of the box are not important. In the center of the lid of the cardboard box, cut a hole to mount the lens. Then glue the lens in place 

• At the centre of the bottom of the box, cut a hole slightly larger than your slides.       
•  For the rear part of the projector, take the second box and make a hole in the bottom of this box of the same size as the hole in the front box. The two holes should line up with each other when the boxes are placed on their sides.

                     

• Join the two boxes by gluing the pieces of cardboard to the sides. Leave a small gap between the boxes for the slide carrier. 

                  

• Make the slide holder from a piece of thick cardboard. This is used to position a slide between the holes in the boxes. 

                        

                 

•  Set slide between two box.

• In a darkened room, project the slide on to a white paper or white wall by switching on the bulb. To get a sharp picture, adjust the focus by pulling out or pushing in the deep lid that holds the lens. 

               

-: MAKING A PERISCOPE :-

A periscope is an optical instrument with which a person can see around corners and other obstractions. It consists of a long tube with a reflecting mirror or prism at each end. The reflecting surfaces are parallel to one another. They are arranged at an angle of 45⁰  inside the tube. Periscopes are important instruments used in submarines and tanks. They are also used by soldiers in the battlefield.

-: MATERIALS REQUIRED :-

• Take a cardboard tube and two small mirrors. Use a small hacksaw to cut a section near each end of the tube. First make a horizontal cut to about 3/4 of the diameter of the tube. Now make two cuts at 45⁰ to the horizontal cuts. Use a 45⁰  set-square for guidance while making these cuts. 

• Glue the mirrors in places where the sloping cuts have been made. The silvered surfaces of the mirror should face each other so that light can pass through the instrument.