In the photoelectric effect, suppose that the intensity of the light is increased, while the frequency is kept constant. The frequency is greater than the minimum frequency f0. State whether each of the following will increase, decrease, or remain constant, and explain your choice.
(a) the current in the phototube
____increase
____decrease
____remain constant
(b) the number of electrons emitted per second from the metal surface
_X___increase
_____decrease
_____remain constant
(c) the maximum kinetic energy that an electron could have
____increase
____decrease
__X__remain constant
(d) the maximum momentum that an electron could have
____increase
____decrease
____remain constant
(e) the minimum de Broglie wavelength that an electron could have
____increase
____decrease
____remain constant
I have figured out the answer to b and c but I am unsure of the reason. Please explain this problem for me please so that I solve this problem. I am sure it is real simple. I have been doing physics for hours and nothing is making sense anymore. Please help!!!
a)increase b) correct c) correct
d)KE max value is constant, and so is mass, so momemtum is also
e) minimum de Broglie wavelength goes with maximum momentum, which stays constant
I'm sorry to hear that you're feeling stuck. Let's break down the problem and I'll explain the reasoning behind each answer.
(a) The current in the phototube:
When the intensity of light is increased, more photons are incident on the metal surface in a given time. The intensity of light is directly proportional to the number of photons hitting the metal surface per second. The photoelectric effect is a process where individual photons interact with individual electrons, causing them to be emitted from the metal surface. Therefore, increasing the intensity of light will increase the number of photons hitting the metal surface, resulting in more electrons being emitted. This increase in the number of emitted electrons will lead to an increase in the current in the phototube.
(b) The number of electrons emitted per second from the metal surface:
Similar to the explanation above, increasing the intensity of light will result in more photons hitting the metal surface, which in turn will cause more electrons to be emitted. Therefore, the number of electrons emitted per second from the metal surface will also increase.
(c) The maximum kinetic energy that an electron could have:
The maximum kinetic energy of an electron in the photoelectric effect is determined by the energy of a single photon, which is proportional to its frequency. When the intensity of light is increased while keeping the frequency constant, the energy of each individual photon remains the same. Therefore, the maximum kinetic energy that an electron could have will remain constant.
(d) The maximum momentum that an electron could have:
The maximum momentum of an electron is determined by its maximum velocity, which in turn is determined by its maximum kinetic energy. As explained in (c), when the intensity of light is increased while keeping the frequency constant, the maximum kinetic energy of the electron remains constant. Since momentum is directly proportional to velocity, the maximum momentum that an electron could have will also remain constant.
(e) The minimum de Broglie wavelength that an electron could have:
The de Broglie wavelength of a particle is inversely proportional to its momentum. As explained earlier, the maximum momentum of an electron remains constant. Therefore, the minimum de Broglie wavelength that an electron could have will also remain constant.
I hope this explanation helps clarify the problem for you. Good luck with your physics studies!