Question

(a) What is the minimum angular spread (in rad) of a 627 nm wavelength gold vapor laser beam that is originally 1.31 mm in diameter?

_________rad

(b) If this laser is aimed at a mountain cliff 14.5 km away, how big will the illuminated spot be? (Give the diameter of the spot in meters.)

___________ m

(c) How big a spot would be illuminated on the Moon, neglecting atmospheric effects? (This might be done to hit a corner reflector to measure the round-trip time and, hence, distance. Assume the distance from the surface of the Earth to the surface of the Moon is 3.82 ✕ 10⁸ m. Give the diameter of the spot in kilometers.)

____________km

Answer 1

7 ) we have relation o ~ 1.22 627 X10-9 on 1.22 X 1-31X10 ON 5.884X164 rad b) D=1435 D, olistance blw light beam & Mountain 2xt D final diameter Tano = a D x= Tano XD Da small Tano = radians 3 -4 x 14-5X10 x=0XD = 5.ggu x 10 82532m 3 2x+D = 2(8.532) + (x103 as it is smaller than distance D neglecting 24 C 17.064 m firal diameter is 17.06Ym

x 3.828 108. YOXD = 5.884 V xió 224.468 xiom neglecting thicknes 44.9:5 km = 2x