Light consisting of two wavelengths, ? a = 4.9 x 10 -7 meter and ? b = 5.7 x 10

Question

Light consisting of two wavelengths, ?a = 4.9 x 10-7 meter and ?b = 5.7 x 10-7 meter, is incident normally on a barrier with two slits separated by a distance d. The intensity distribution is measured along a plane that is a distance L = 0.81 meter from the slits as shown above. The movable detector contains a photoelectric cell whose position y is measured from the central maximum. The first order maximum for the longer wavelength ?b occurs at y = 1.3 x 10-2 meter.

a. Determine the slit separation d. m
b. At what position ya does the first order maximum occur for the shorter wavelength ?a? m

In a different experiment, light containing many wavelengths is incident on the slits. It is found that the photosensitive surface in the detector is insensitive to light with wavelengths longer than 5.6 x 10-7 m.

c. Determine the work function of the photosensitive surface. eV
d. Determine the maximum kinetic energy of electrons ejected from the photosensitive surface when exposed to light of wavelength ? = 4.9 x 10-7 m. eV

Light consisting of two wavelengths, ?a = 4.9 x 10-7 meter and ?b = 5.7 x 10-7 meter, is incident normally on a barrier with two slits separated by a distance d. The intensity distribution is measured along a plane that is a distance L = 0.81 meter from the slits as shown above. The movable detector contains a photoelectric cell whose position y is measured from the central maximum. The first order maximum for the longer wavelength ?b occurs at y = 1.3 x 10-2 meter. a. Determine the slit separation d. b. At what position ya does the first order maximum occur for the shorter wavelength ?a? In a different experiment, light containing many wavelengths is incident on the slits. It is found that the photosensitive surface in the detector is insensitive to light with wavelengths longer than 5.6 x 10-7 m. c. Determine the work function of the photosensitive surface. d. Determine the maximum kinetic energy of electrons ejected from the photosensitive surface when exposed to light of wavelength ? = 4.9 x 10-7 m.

Explanation / Answer

1) y=lambda*L/d

==> d=5.7E-7*0.81/0.013= 3.55E-5 m

2) ya=4.9E-7*0.81/3.55E-5 = 1.118 E-2 m

3) work fuction = 1242/lambda(in nm)= 1242/560= 2.2178 eV

3) Max K.E= 1242/490- 2.2178 = 0.317 eV

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