(a) What is the energy in joules of an x-ray photon with wavelength 3.94 10 10 m

Question

(a) What is the energy in joules of an x-ray photon with wavelength 3.94 1010 m?
J

(b) Convert the energy to electron volts.
keV

(c) If more penetrating x-rays are desired, should the wavelength be increased or decreased?

increased decreased    

(d) Should the frequency be increased or decreased?

increased decreased   



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 2.51 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. (Assume the radius of the Earth and the Moon are 6380 km and 1740 km respectively.)
m/s

Explanation / Answer

E = hf = hc/L, where:

h:Plancks' constant, c:lightspeed, L:wavelength

E = (6.626x10-34)(3x10^8)/(3.94 *10-10 )

= 5.045x10-16 J , but 1eV = 1.6x10^-19J so that

E = 5.045x10-16(1/1.6x10-19) = 3.153 KeV

If more penetrating x-rays are desired, should the wavelength be increased

Should the frequency be increased

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