1) During the Apollo XI Moon landing, a retroreflecting panel was erected on the

Question

1)

During the Apollo XI Moon landing, a retroreflecting panel was erected on the Moon's surface. The speed of light can be found by measuring the time it takes a laser beam to travel from Earth, reflect from the panel, and return to Earth. If this interval is found to be 2.503 s, what is the measured speed of light? Take the center-to-center distance from Earth to Moon to be 3.84 108 m. Assume that the Moon is directly overhead and do not neglect the sizes of the Earth and Moon.

_______m/s

2)

(b) Convert the energy to electron volts. _______eV

Explanation / Answer

1.

radius of earth =r1= 6.37*10^6m

Radius of moon = r2= 1.74*10^6 m

Total distance from earth to moon = d = (3.84*10^8) – (r1+r2) = (3.84*10^8) – (6.37*10^6+1.74*10^6) = 3.76*10^8 m

v= 2d/t = (2*3.76*10^8)/2.503 = 3*10^8m/s

2.

a)Use the equation E = hv,

where h = Planck's constant = 6.626 * 10^-34 J.s

v = frequency = c/ ………………….where c is the speed of light, 3.00 * 10^8 m/s.

E= hc/ = (6.626 * 10^-34*3.00 * 10^8)/(3.90*10^-9) = 5.1*10^-17 J

b) 1J = 6.24*10^18 eV

5.1*10^-17 J= 5.1*10^-17* 6.24*10^18 eV = 318.24 eV

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