Laser Pointers are a measurement, leveling, and calibration (SLA) laser product in accordance with section 1040.11(b) of 21CFR of FDA's center for devices and radiological health (CDRH). CDRH laser grade restriction for SLA laser products, including laser pointer, belongs to grade IIIa. CDRH also recognizes IEC 60825-1 grade 3R, which is equivalent to CDRH Grade IIIa. These CDRH and IEC 60825-1 green laser pointer classes are equivalent to laser power not exceeding 5mW. Laser power exceeding 5mW is extremely dangerous and can cause potential hazards such as temporary vision problems or eye damage.
Therefore, any laser pointer emitting radiation in excess of Grade IIIa/3R May not be imported into the United States or sold or marketed within the United States. Retailers selling laser Pointers (made by other companies) can also use laser pointer safety test reports to prove that their products meet US CDRH or other global requirements for laser safety. It's impossible to break a glass with a laser pointer. The glass has a high reflectivity and penetration rate of the laser. Only a small fraction of the laser energy can be absorbed by the glass, and the laser pointer is not powerful enough. Military laser weapons could do it, but no one's tried it, so I'm not sure. If you can really make the glass broken, it is caused by uneven thermal expansion and contraction caused by heat broken. It is also possible for a high-energy laser pointer to instantly vaporize or melt glass, rather than shatter it.
At present, English teaching basically has adopted the blackboard and projector combined teaching method, using the blackboard and multimedia teaching method can deepen the students' understanding of the teacher's lecture content, improve the quality of teaching. In the use of blackboard teaching, the teacher needs to draw four lines on the blackboard for blackboard writing; When using the projector, the teacher has to use the computer, mouse and laser pointer.
