USING LASERS SAFELY To date no eye damage has been reported in the Physics Depar

Question

USING LASERS SAFELY To date no eye damage has been reported in the Physics Department. Hopefully your careful use and respect of the lasers used in LAB Y2 will allow this situation to continue. Please read on.... HOW BRIGHT IS A LASER? Our Helium-Neon lasers produce light power of about 1 milliwatt over an area of about 1 mm^2. The power per unit area is therefore 10-3 W / 10-6 m2 = 1000 W/m2. Our solid state lasers (frequently called ``laser pointers") produce 3 to 5 times as much power, however the angle of the beam is larger, making the power per m2 about the same as for our Helium-Neon lasers. A comparable figure for the Sun is the solar constant. It is about 1350 W/m2 (measured at the equator, for an average Earth to Sun distance). Our lasers are thus about as bright as the noon-day Sun!!! For more details, read ``Just How Bright is a Laser" by David Van Baak. This article is posted in Room 201. You can also find it in Physics Teacher, Nov. 1995, p. 497. Please think about the statements listed below and select all the correct ones.

E.g., if A and C are correct, enter AC.

A- Avoid looking at reflections of laser light from jewellery and other shiny objects.Remove such objects beforehand. Laser reflections from dull surfaces, such as paper, wood should be harmless.

B-Laser tag is a harmless game (especially when no one is wearing eye protection) and will be tolerated by the demonstrators.

C-Never look directly into a laser beam.

D-Momentary flashes of laser light are less harmful than prolonged exposure.

Explanation / Answer

In mirror-like reflections, the laser light reflection intensity remains unchanged.

So, the answer is ACD

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