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Laser Pointers

A laser pointer is a small (often battery-operated) laser device designed for pointing at objects by illuminating them with a collimated visible laser beam. Most laser pointers, particularly the cheap ones, contain a small GalnP/AIGaInP laser diode operating somewhere in the red spectral region. Some significantly more expensive pointers emit green or even blue light and normally contain a small diode-pumped solid state laser with a nonlinear crystal for frequency doubling.
A typical use of a hand-held laser pointer is to point at some screen or chart during a presentation, e.g. a conference talk. This is convenient because it can be done from a large distance and requires only a rather small device. However, the visibility of the generated spot on the screen is often poor (particularly for red laser pointers with relatively long emission wavelength), and a fast moving light spot can h
A. By giving warnings under different occasions.
B. By listing some standards that the manufactures should follow.
C. By comparing different types of lasers.
D. By demonstrating the side-effects of lasers.