P1 The electromagnetic spectrum

P1 The electromagnetic spectrum

1. the discovery of waves outside the visible spectrum

   • Isaac Newton discovered the visible spectrum
     • the colours of the visible spectrum are red, orange, yellow, green, blue, indigo, violet
   • William Herchel discovered infrared waves
     • he discovered it by measuring the temperature of the different colours of the visible spectrum, and found that the area after the red was the warmest
   • Johann Ritter discovered ultraviolet waves
     • he realised that when he preformed the reaction of sodium chloride (silver chloride breaks down into black silver when exposed to light) the reaction was vastest after the violet
   • Heinrich Hertz discovered radio waves
     • sent a signal across his laboratory
   • Wilhelm Rontgen discovered X-rays
   • Paul Villard discovered gamma rays

2. uses of electromagnetic waves

   • radio waves: transmitting television, radio programs, communication and satellite transmitions
   • microwaves: satellite communication, mobile phones and cooking
   • infrared: grills, toasters, heaters, remote controls (short range), optical fibre com, muscular treatment, thermal imaging, security systems
   • visible light: vision, photography, illumination
   • ultraviolet: florescent lamp, security coding, sunbeds, detecting forged notes, disinfecting water
   • X-rays: shadow pictures of bones and metals (medical X-rays), airport security
   • gamma rays: detecting and killing cancer cells, killing bacteria on food, sterilising surgical equipment