What is the intensity of the electromagnetic radiation at a distance of 2.00 m from a 100 W isotropic source?
a. 
b. 
c. 
d. 
e. 
d.
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Synchrotron radiation is produced
a. in planetary nebulae. b. by red dwarfs. c. in massive stars as their iron core collapses. d. in supernova. e. by neutrinos.
A molecule of roughly spherical shape has a mass of 6.10 × 10-25 kg and a diameter of 0.70 nm. The uncertainty in the measured position of the molecule is equal to the molecular diameter
What is the minimum uncertainty in the speed of this molecule? (h = 6.626 × 10-34 J ? s) A) 0.78 m/s B) 7.8 m/s C) 78 m/s D) 0.078 m/s E) 0.0078 m/s
How does a black hole form from a massive star?
A) During a supernova, if a star is massive enough for its gravity to overcome neutron degeneracy of the core, the core will be compressed until it becomes a black hole. B) Any star that is more massive than 8 solar masses will undergo a supernova explosion and leave behind a black-hole remnant. C) If enough mass is accreted by a white dwarf star so that it exceeds the 1.4-solar-mass limit, it will undergo a supernova explosion and leave behind a black-hole remnant. D) If enough mass is accreted by a neutron star, it will undergo a supernova explosion and leave behind a black-hole remnant. E) A black hole forms when two massive main-sequence stars collide.
Heat transfer that involves mass movement is
a. temperature. b. conduction. c. convection. d. radiation.