23. Monochromatic light of wavelength lambda strikes a clean metal surface. Elec

Question

23. Monochromatic light of wavelength lambda strikes a clean metal surface. Electrons are ejected from the metal surface arid reach a second metal plate (held at a voltage V with respect to the illuminated metal surface) where the electron current arid electron kinetic energy can be measured. If the intensity of the light is increased without changing the wavelength, what will happen to the ejection rate and maximum energy of the electrons? A. lower electron ejection rate; same maximum energy B. greater electron ejection rate; same maximum energy C. greater electron ejection rate; greater maximum energy D. same electron ejection rate; greater maximum energy E. same electron ejection rate; same maximum energy 24. In a particular version of the apparatus described in Question 23 the illuminated metal surface is made of silver which has a work function of 4.26 eV and the voltage V is adjusted to be -0.3 volts. What are the wavelengths of monochromatic light that will enable an electron current to be measured on the second metal plate? A. up to 272 nm B. up to 313 nm C. down to 272 nm D. down to 313 nm E. between 272 nm and 313 nm

Explanation / Answer

Intensity of light doesn't affect kinetic energy of ejected electrons

Inceasing intensity increases ejection rate

23)

Answer is

B) greater ejection rate , same maximum kinetic energy

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24)

Work Function = W = 4.26 eV

Voltage adjusted to - 0.3 V

lambda = h c / E = 6.63 x 10^-34 x 3 x 10^8 / ( 4.56 x 1.6 x 10^-19 ) = 272 nm

lambda 2 = h c / E = 6.63 x 10^-34 x 3 x 10^8 / ( 3.96 x 1.6 x 10^-19 ) = 313 nm

Answer is

Option E) between 272 nm and 313 nm

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