The speed of an electromagnetic wave is given by c = lambda f. What happens to t
ID: 1281727 • Letter: T
Question
The speed of an electromagnetic wave is given by c = lambda f. What happens to the speed of the wave when you double its frequency? You stand 1 .00 meter in front of your bathroom meter and wink. How long does it take for you to notice that good-looking person in the mirror winking at you? Determine the critical angle for the air-water interface. Why does your voice seem to sound better than usual when you sing in the shower? At a particular point the electric field of an electromagnetic wave has an amplitude of 6.0 kV/m and points in the + y direction, while the magnetic field points in the - z direction. What is the propagation direction, wave speed, and the amplitude of the magnetic field?Explanation / Answer
1) speed doesnt change since its a constant
2. light has to go to the mirrorand back so d = 2m
t = d/v = 2/3.0E8= 6.67E-9 s
3)
sin thetacritical = 1/1.33
theta = arcsin(1/1.33)= 48.75 degrees
4) because you are in an enclosed space and your voice can bounce off the walls and resonate
5)
so right hand rule for direction, y into -z gives -x
so direction is -x
speed is c = 3.0E8 m/s
c B = E
so B = E/c = 6.0E3/3.0E8= 2.0E-5 T
6)
1/p + 1/q = 1/f
1/.25 + 1/(1.6-0.25) = 1/f
f=0.211 m
7) speed = c/n = 3.0E8/1.473= 2.037E8 m/s
wavelength = speed/f = 2.037E8/5.09E14=4.00E-7 m = 400 nm
8) average value = intensity = P/A = 250.0E3/(4*pi*8.0E3^2) = 3.11E-4 W/m^2
9) No since it will bend back exactly the way it bent when going in
since n1 sin theta 1 = n2 sin theta 2
at both interfaces
so theta1 -> theta2
but it will also be theta2 on other side so it will go back to theta1
10)
Pressure absorb = I/c
Pressure reflect = 2I/c
so Pressure = 0.5 I/c + 0.5*2I/c = 1.5 I/c
I = P/A
Pressure = 1.5*(3.0E-3/(pi*1.0E-3)^2)/3.0E8= 1.52E-6 N/m^2
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