Question

An ultraviolet source produces a monochromatic beam of 200-nm light. A shutter allows a pulse to pass that is 10,000 wavelengths long. The uncertainty in the energy of a photon in this pulse is closest to which of the following? , c = 3.00 × 108 m/s)

Answer 1

= wavelength of the monochromatic beam = 200 nm = 200 x 10^-9 m

t = duration of the pulse = number of wavelengths/speed of beam = 10000 x 200 x 10^-9 /(3 x 10⁸) = 2 x 10^-11 /3

E = uncertainty in energy

Using the equation

E  t = h/(2)

E (2 x 10^-11 /3) = (6.63 x 10^-34)/(2(3.14))

E = 1.6 x 10^-23 J

E = 1.6 x 10^-23 /(1.6 x 10^-19) eV

E = 1 x 10^-4 eV