It has become a tradition at Beccles U3A for the monthly meeting to be followed by a Guest Speaker. As you will see from the list below, the subjects are very varied. With topics ranging from cake icing to Stonehenge, they are not to be missed.
The monthly talk takes place immediately after the Monthly Meeting on the 3rd Wednesday of each month at 10.30 at Beccles Public Hall.
How lasers work – the light fantastic. Dr. Stephen Ashworth
Dr. Stephen Ashworth, a Senior Lecturer UEA, delivered an extremely entertaining and informative presentation on the subject of lasers and how they work. He incorporated a series of practical demonstrations throughout his talk and managed to explain this somewhat complex subject in terms we could all understand.
“Laser” is an acronym for light amplification by stimulated emission of radiation.
A laser is created when the electrons in atoms in special glasses, crystals, or gases absorb energy from an electrical current or another laser and become “excited.” The excited electrons move from a lower-energy orbit to a higher-energy orbit around the atom’s nucleus. When they return to their normal or “ground” state, the electrons emit photons (particles of light).
These photons are all at the same wavelength and are “coherent,” meaning the crests and troughs of the light waves are all in step. In contrast, ordinary visible light comprises multiple wavelengths and is not coherent.
Laser light is different from normal light in other ways. First, its light contains only one wavelength (one specific color). The particular wavelength of light is determined by the amount of energy released when the excited electron drops to a lower orbit. Second, laser light is directional. Whereas a laser generates a very tight beam, a flashlight produces light that is diffuse. Because laser light is coherent, it stays focused for vast distances, even to the moon and back.
The first working laser was a ruby laser made by Theodore H. "Ted" Maiman at Hughes Research Laboratories in 1960. Some lasers, such as ruby lasers, emit short pulses of light. Others, like helium–neon gas lasers or liquid dye lasers, emit light that is continuous. Laser light does not need to be visible.
Lasers are now used in optical disk drives, laser printers, barcode scanners, DNA sequencing instruments, fibre-optic communications, laser surgery and skin treatments, cutting and welding materials, military and law enforcement devices for marking targets and measuring range and speed, and in laser lighting displays for entertainment. Research is also taking place into potential usage in the healthcare arena such as helping ‘clean’ arteries of plaque.
Below is an explanation of how ruby lasers work.
A ruby laser consists of a flash tube (like you would have on a camera), a ruby rod and two mirrors (one half-silvered). The ruby rod is the lasing medium and the flash tube pumps it.
Thank you Vicki John for writing this report
Up and coming talks
Wed 20 March 2019:- Sally Dearman Women CAN fly - a female pilot talks of her experiences
Wed 17 April 2019: Jim Graver The Big Issue
Wed 15 May 2019: Dawn Blunden Cake Icing for Royal Weddings
Wed 19 June 2019: Jenny Gibbs A Turkish Shirley Valentine
Wed 17 July 2019# Joy Hawkins: returning by popular request More Medieval Medicine
Wed 21 August 2019: Garden Bird Watch
Wed 18 September 2019: Ann Jillings and Varley the dog Dogs For The Deaf
Wed 16 October 2019: Ronald Binns George Orwell and Southwold
Wed 20 November 2019: Lionel Simms Decoding Stonehenge_ TBC
Review Past Monthly Talks