physics....
posted by kennedy on .
1) Yellow light that has a wavelength of 560 nm passes through two narrow slits that are 0.300 mm apart. An interference pattern is produced on a screen 160 cm distant. What is the location of the firstorder maximum?
2) A communication satellite is orbiting 36 000 km above Earth’s surface. Two cities, 3500 km apart are transmitting to and receiving signals from each other. Find the time required to transmit a signal from one city to the other. They are equidistant from the satellite.

x(min) =±(2k1)•λL/2•d,
x(min1) =λL/2•d =560•10^9•1.6/2•0.3•10^3 =1.49•10^3m =1.49 mm
s=2•sqrt{(3.6•10^7)²+(3.5•10^3)²} =7.2•10^4.
t=s/c=7.2•10^4/3•10^8=0.24 s. 
I don't understand why you're multiplying by two for the second question.

nevermind I get it