Light-emitting diodes (LEDs) in a classroom demonstration kit produce light of…
PHYSICS · Multi-part · A Level · Physics · Particles and radiation · Particles and radiation
Problem
Light-emitting diodes (LEDs) in a classroom demonstration kit produce light of different colors. One yellow LED is specified to emit photons with an average energy of exactly 2.10 eV.
1 eV = 1.602×10−19J
(a) Convert the photon energy of the yellow LED to joules. Show your calculation.
(b) Determine the wavelength, in nanometers, corresponding to photons of this energy.
(c) The kit also contains a blue LED that emits light at 470 nm and a red LED that emits light at 630 nm. Rank the yellow, blue, and red LEDs from highest to lowest photon energy and support your ranking with numbers.
(d) If an experiment requires photons of at least 2.90 eV each, explain whether any of the three LEDs in the kit can be used. Cite quantitative evidence in your answer.