Photons

Question 1

EM waves

Answer 1

• 3.00 x 10^8 m/s in a vacuum
• lambda = speed of light in vacuum / frequency
• Em wave = electric wave & magnetic wave, travel & vibrate together
• Oscillate at 90° to direction of energy transfer
• In phase, both waves reach same peak together

Question 2

Photons

Answer 2

• Emitted by charged particle when looses energy
• Fast moving electron stopped / slows down / direction change
• Electron in shell of atom moves to different shell of lower energy
• Em waves emitted in short burst, different directions (photon)
• Photoelectric effect: emission of electrons from metal surface when light directed at surface
• E=hf

Question 3

Lasers

Answer 3

• Consist of photons of same freq
• Power of beam = energy / sec transferred by photons
• Power of beam = nhf (n = number of photons in beam passing fixed point)