Using a Laser or Light Source (OCR A Level Physics)

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Using a Laser or Light Source

  • A laser or light source is used to investigate characteristics of light such as interference and diffraction
  • A laser is preferred to a lamp since they produce coherent, monochromatic light
    • This produces a sharper and brighter interference pattern

  • The contrast between the bright and dark fringes is much easier to see in laser light, compared to a lamp with a low intensity that emits light of all wavelengths
  • In experiments such as Young's double-slit experiment, it is important to be able to see the fringes clearly to determine the fringe width
    • If these were not clear, there will be a large error in the measurement of the fringe widths

Diffraction with a laser, downloadable AS & A Level Physics revision notes

Single slit diffraction of a laser producing an interference pattern on the screen

Safety Issues with Lasers

  • Lasers produce a very high energy beam of light
  • This intense beam can cause permanent eye damage or even blindness
  • In schools, only class 2 lasers are allowed - these are lasers with a power output of less than 1 mW
    • However, more powerful lasers can reach outputs of more than 500 mW
    • These are known as class 4 lasers. They are so powerful they can make a person instantly blind and can even damage the skin

Eye Injury Hazard, downloadable AS & A Level Physics revision notes

The four classes of laser: In a school laboratory, only Class 2 lasers may be used

Precautions with Lasers

  • It's important to use lasers safely and follow the guidelines in all practicals:
    • Never look directly at a laser or its reflection
    • Don’t shine the laser towards a person
    • Don't allow a laser beam to reflect from shiny surfaces into someone else's eyes
    • Wear laser safety goggles
    • Place a ‘laser on’ warning light outside the room
    • Stand behind the laser

Laser Warning, downloadable AS & A Level Physics revision notes

Placing a laser warning sign outside of the door is one precaution that can be taken when using lasers

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Ashika

Author: Ashika

Expertise: Physics Project Lead

Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.