QUES: After Germany invaded the Soviet Union on 22 June 1941, the Wehrmacht crossed the Estonian southern border on 7 July. The Red Army retreated behind the Parnu River Emajogi line on 12 July. At the end of July the Germans resumed their advance in Estonia working in tandem with the Estonian Forest Brothers. Both German troops and Estonian partisans took Narva on 17 August and the Estonian capital Tallinn on 28 August. After the Soviets were driven out from Estonia, German troops disarmed all the partisan groups.

When did the Werhmacht cross south border of Estonia?
What is the answer?
ANS: 7 July
QUES: It is said[by whom?] on one side of this debate that separation of powers means that powers are shared among different branches; no one branch may act unilaterally on issues (other than perhaps minor questions), but must obtain some form of agreement across branches. That is, it is argued that "checks and balances" apply to the Judicial branch as well as to the other branches.

What term is used when one branch of government must get approval from at least one other branch of government?
What is the answer?
ANS: checks and balances
QUES: Lasers emitting in the green part of the spectrum are widely available to the general public in a wide range of output powers. Green laser pointers outputting at 532 nm (563.5 THz) are relatively inexpensive compared to other wavelengths of the same power, and are very popular due to their good beam quality and very high apparent brightness. The most common green lasers use diode pumped solid state (DPSS) technology to create the green light. An infrared laser diode at 808 nm is used to pump a crystal of neodymium-doped yttrium vanadium oxide (Nd:YVO4) or neodymium-doped yttrium aluminium garnet (Nd:YAG) and induces it to emit 281.76 THz (1064 nm). This deeper infrared light is then passed through another crystal containing potassium, titanium and phosphorus (KTP), whose non-linear properties generate light at a frequency that is twice that of the incident beam (563.5 THz); in this case corresponding to the wavelength of 532 nm ("green"). Other green wavelengths are also available using DPSS technology ranging from 501 nm to 543 nm. Green wavelengths are also available from gas lasers, including the heliumneon laser (543 nm), the Argon-ion laser (514 nm) and the Krypton-ion laser (521 nm and 531 nm), as well as liquid dye lasers. Green lasers have a wide variety of applications, including pointing, illumination, surgery, laser light shows, spectroscopy, interferometry, fluorescence, holography, machine vision, non-lethal weapons and bird control.

What is the THz of the helium-neon laser?
What is the answer?
ANS:
unanswerable