Question

Photoelectrons come out when a metal is radiated by indigo but not by green light. Would photoelectrons come out when the metal is radiated by orange light?
A. Yes
B. No
C. Yes if the intensity of radiation is increased
D. Yes if the metal is radiated for a long time

Answer 1

Photoelectric effect is the emission of electrons from the surface of a metal when it absorbs of photon or EM wave of optimum energy. The minimum energy required by a surface for the emission of an electron is called the work function corresponding to the work function; there is a threshold to the frequency below which the emission of the photoelectron won’t take place. The visible spectrum of light is also the Electromagnetic Wave. The order of their frequency is
Violet > Indigo > Blue > Green > Yellow > Orange > Red.
Formula Used: $E=h{{v}_{0}}$

Complete answer:
Photoelectric effect is the emission of electrons from the surface of a metal when it absorbs a photon or EM wave of optimum energy. These emitted electrons are called the photoelectrons. For the emission of these photoelectrons the energy of the photon absorbed must be higher than the binding energy of that electron. This minimum energy required for the emission of an electron is called work function.
The energy of an electromagnetic wave or photon is related to its frequency. The higher the frequency of the photon the higher the energy. So, corresponding to the work function there is a threshold to the frequency below which the emission of the photoelectron won’t take place. This relation is shown as
$E=h{{v}_{0}}$, here ${{v}_{0}}$ is called the threshold frequency and E is called the work function.
The visible spectrum of light is also the Electromagnetic Wave. The order of their frequency is
Violet > Indigo > Blue > Green > Yellow > Orange > Red. The energy corresponding to these photons would be in the same order.
Coming to the question, photoelectrons are emitted by indigo but not by green. So, the threshold frequency of the metal is higher than the frequency of green. So, for any photon of frequency lower than green photoemission will not take place and as orange has a lower frequency than that if green so photoelectrons will not come out when the metal is radiated by orange light.

So, Option B is the correct answer.

Note:
Photoemission takes place by absorption of a single photon. If the energy of that one photon is higher than the work function then photoemission will take place. And since the emission takes place by absorption of a single photon the number of photons incident does not matter and hence the intensity of the incident EM wave does not matter for photoelectric emission.