A spacecraft is powered by electricity generated by the heat produced when 23894Pu decays with a half-life of 87.75 y. Engineers predict that the spacecraft will have insufficient power to operate its instruments when the amount of 238 94Pu in its power generators drops below 67 % of the amount it had at launch on September 1, 1977 Required:
In what year will its instruments cease to function?

Which of the following are considered noble gases? a. bromine b. neon c. argon d. chlorine

Two loudspeakers, 5.5 m apart and facing each other, play identical sounds of the same frequency. you stand halfway between them, where there is a maximum of sound intensity. moving from this point toward one of the speakers, you encounter a minimum of sound intensity when you have moved 0.33 m . assume the speed of sound is 340 m/s. part a) what is the frequency of the sound? part b) if the frequency is then increased while you remain 0.21 m from the center, what is the first frequency for which that location will be a maximum of sound intensity? express your answer to two significant figures and include the appropriate units.

Amajor difference radio waves, visible light, and gamma rays is the of the photons, which results in different photon frequencies and wavelengths