PD Ravindra, a 77-year-old retired engineer and innovator, runs a free museum in Bengaluru.

He aims at giving children an understanding of scientific principles using simple examples and showcasing the various uses of inexpensive waste materials.

The museum houses a kaleidoscope, a periscope, a shuttle launcher, a bubble maker, a hovercraft model, and a wave pendulum, among other things.

Source: Inshorts