A photoelectric material has a threshold wavelength of

PHYSICS · Multi-part · CBSE · Physics · Dual Nature of Radiation and Matter · Dual Nature of Radiation and Matter

Problem

570\,\text{nm}

. Monochromatic light beams of the following wavelengths are shined one at a time onto the material with identical intensities: •

650\,\text{nm}

(labeled “red”) •

580\,\text{nm}

(labeled “yellow”) •

530\,\text{nm}

(labeled “green”) •

400\,\text{nm}

(labeled “violet”) (a) Rank the four beams by photon energy from lowest to highest. (b) Identify which beam(s), if any, will successfully eject electrons from the material. Justify your answer using the threshold information provided. (c) For the beam with the greatest photon energy, calculate the frequency of its photons and explain how this value relates to your ranking in part (a). (d) Suppose the intensity of the

530\,\text{nm}

beam is doubled while its wavelength is unchanged. Explain qualitatively what effect, if any, this change has on the photon energy ranking you established in part (a).

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