3.3.2.1
Lasers are coherent and monochromatic -- with safety rules
Interference & Diffraction — AQA A-Level Physics
- Lasers produce coherent (constant phase differenceThe fraction of a cycle by which one wave leads or lags behind another, measured in degrees or radians., same frequencyThe number of complete oscillations passing a point per unit time. Measured in hertz (Hz).) and monochromatic (single wavelengthThe minimum distance between two points on a wave that are in phase (e.g. crest to crest). Measured in metres (m).) light.
- This makes them ideal for producing clear interference patterns.
- Non-coherent sources (filament bulbs, sodium lamps) produce white light and blurry patterns.
Laser safety precautions
- Never look directly at a laser beam or its reflection.
- Do not shine a laser towards a person.
- Remove reflective surfaces from the experimental area.
- Wear laser safety goggles.
- Place a 'laser on' warning sign outside the room.
- Stand behind the laser during use.
- Lasers should be Class 2 with a maximum output of 1 mW.