very short pulses of high-intensity laser beams are used to repair detached port

Question

very short pulses of high-intensity laser beams are used to repair detached portions of the retina of the eye. The brief pulses of energy absorbed by the retina welds the detached portion back into place. In one such procedure, a laser beam has a wavelength of 827nm , and delivers 291mW , of power spread over a circular spot 516?m , in diameter. The vitreous humor (the transparent fluid that fills most of the eye) has an index of refraction of 1.34.

What is the frequency of the laser light inside the vitreous humor of the eye?

What is the maximum value of the electric field in the laser beam?

What is the maximum value of the magnetic field in the laser beam?

Explanation / Answer

Here,

as speed = frequecy * wavelength

3 *10^8 = 827 *10^-9 * frequency

frequency = 3.627 *10^14 Hz

the frequency of the light stays the same for all the mediums

Hence, the frequecny of light in eye is 3.627 *10^14 Hz

B)

intensity = 291 *10^-3/(pi*(516*10^-6/2)^2)

Intensity = 1.392 *10^6 W/m^2

Now , as I = 0.5*Em^2/(c*u0)

1.392 *10^6 = 0.5 * Em^2 /(3*10^8 * u0)

Em = 3.24 *10^4 N/C

the maximum electric field is 3.24 *10^4 N/C

C)

Now,

Bm = Em / C

Bm = 3.24 *10^4 /3*10^8

Bm = 1.08 *10^-4 T

the maximum magnetic field is 1.08 *10^-4 T

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