(a) What is the minimum angular spread of a 555 nm wavelength He-Ne laser beam t

Question

(a) What is the minimum angular spread of a 555 nm wavelength He-Ne laser beam that is originally 1.00 mm in diameter? rad ( lE-6 rad) A telescope can be used to enlarge the diameter of a laser beam and limit diffraction spreading. The laser beam is sent through the telescope in opposite the normal direction and can then be projected onto a satellite or the Moon. (b) If this is done with the Mount Wilson telescope, producing a 2.54 m diameter beam of the same wavelength He-Ne laser light, what is the minimum angular spread of the beam? rad ( lE-9 rad) (c) Neglecting atmospheric effects, what is the size of the spot this beam would make on the Moon, assuming a lunar distance of 3.84x108 m? m ( 1 m)

Explanation / Answer

here,

theta = 1.22 * Lamda/Dia

A)
lamda = 555 nm = 555 * 10^-9 m
Dia = 1 mm = 0.001 m

Theta = (1.22 * 555 * 10^-9) / 0.001
Theta = 6.771 * 10^-4 rad

B)
lamda = 555 nm = 555 * 10^-9 m
Dia = 2.54 m

Theta = (1.22 * 555 * 10^-9) / 2.54
Theta = 2.6657 * 10^-7 rad

C)

R = 3.84 * 10^8 m

distance s between two objects a distance r away and separated by an angle is
s = r*Theta
s = 3.84 * 10^8 * 2.6657 * 10^-7
s = 102.363 m

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