In 1999, a group at MIT slowed light to a speed of lcm/s in sodium gas Compute t

Question

In 1999, a group at MIT slowed light to a speed of lcm/s in sodium gas Compute the index of refraction. (Note, the same techniques have been used to stop light, bet that doesn't make a good problem). What is the relation if any. between the direction of the electric component and the magnetic component of an electromagnetic wave? There is no general relation between the direction of the electric and magnetic component of an electromagnetic wave The electric and magnetic components are parallel The electric and magnetic components are perpendicular The electric and magnetic components make an angle of 45 degree with each other The Planetary Society's light sail, that we discussed in lecture has a mass of 100 kg and a sail area of 600m^2. We found a very boring accelerate for sunlight in near-earth orbit To mate the sad accelerate faster we shine lasers on it from earth Assume the laser completely illuminate the sail area, all 600m^2, and that the sail is perfectly reflecting What must the intensity of the light be at the sail to produce an acceleration of g = 9.81 ? Don't forget the 2 for perfectly reflecting.

Explanation / Answer

1) refractive index n = c/v

here v = 1 cm/sec = 0.01 m/sec

n = 3*10^8/0.01 = 3*10^10 m/sec

2) in the propagation of electro magnetic wave both electric and magnetic field s are perpenducular to each other

3) intensity = power/area = mg*c/A

intensity = 100*9.8*3*10^8/600 = 4.9 *10^8 W/m^2

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