Lala Lajpath Rai along with Madan Mohan Malavya founded the Nationalist Party
- A wave from which travels at a constant speed of 300000000 m/s and is unaffected by electric or magnetic fields, such that it needs no material for its propagation is called electromagnetic wave.
- Light waves are transverse electromagnetic waves.
- Radio waves, television waves, microwaves, infra-red ray, visible light, ultraviolet rays, x-rays and gamma rays are major parts of electromagnetic spectrum in the order of decreasing wavelength or increasing frequency.
- Radio waves, TV waves and micro-waves are produced by oscillating circuits in special vaccum tubes.
- Infra-red rays, visible radiation and ultra-violet rays are produced by the excitation of outer electronic shell in increasing order.
- X-rays are produced by the excitation of inner electrons of an atom and sudden destruction of high energy free electrons.
- Gamma radiation are produced by the nucleus of an atom by the sudden destruction of high energy particles. They find use in the cure of cancer.
- The regions of spectrum which do not excite retina and hence are not visible are collectively canned invisible spectrum. Infra-red and ultra-violet radiations are parts of it.