All but one of the following are necessary to create a functioning laser through stimulated emission. Which one is not necessary?
1.The system must consist of a stable gas.
2.The system must primarily be in an excited state.
3.The excited state must be metastable.
4.It must be possible for the emitted photons to stay within the system long enough to stimulate the emission of other photons.
1
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Lens-Maker Formula: A plano-convex lens is to have a focal length of magnitude 40 cm, and it is made of glass of index of refraction 1.65. What radius of curvature is required?
A. 13 cm B. 26 cm C. 32 cm D. 36 cm
How many degrees as measured on the celestial sphere does the Moon cover as it moves during the course of one day?
5 degrees 36 degrees 13 degrees 25 degrees
What is the limiting angle of resolution for a lens of radius 2.0 mm when viewing with light having a wavelength of 600 nm?
A) 1.8 × 10-7 rad B) 1.3 × 10-4 rad C) 1.5 × 10-7 rad D) 1.5 × 10-4 rad E) 1.8 × 10-4 rad
The nuclei of radioactive isotopes can sometimes give off
A) visible radiation B) UV rays C) gamma rays D) X-rays