How does the photoelectric effect suggest the particle-like nature of light?

[vangto]

I have my final exam coming up on tuesday and I've been going over past examinations. I mainly have problems with E &M and the particle/wave nature of light. I have some questions that I wasn't able to answer myself that I was hoping people could help me out with.

1. Why does the photoelectric effect suggest that light has particle-like
properties? Orange light can generate photoelectrons from the metal potassium,
but red light cannot. Name another color of light which can produce the
photoelectric effect in potassium and explain your answer.

2. Why do the magnetic field lines outside of an isolated bar magnet never
cross?

3. What does the double slit experiment using electrons tell us about the
wave and particle nature of electrons?

4. Can atoms ever be at rest? Answer this question from the point of view of
classical and quantum mechanics. Think about cooling a gas of atoms to near
absolute zero temperature.

5. What is the perihelion shift of the planet Mercury? How does the
measurement of this quantity support the predictions of the General Theory of Relativity?

for this last question, I know that the perihelion is the closest point of a planets orbit to the sun. I also know that the axis of perihelion shifts slowly over time. Basically I do not know why, and how it is related to general relativity.

Thanks in advance for any help that can be offered.

 

[OlderDan]

Too late to touch on all those topics, but I'll do one paragraph on the first one. In wave theory, the energy of the light is related to the intensity. Bright light has a lot of energy; dim light has little energy. In the photelectric effect, no matter how bright the red light is it cannot induce potassium to give up any electrons. Yet even a dim orange light causes some photoelectrons to be released, and the number of phototelectrons increases with the intensity of the orange light. This suggests that light energy can only be absorbed in discrete amounts, and that it can only be absorbed if one "quantum" of energy is sufficient to release an electron. A lot of quanta with sufficient energy will release a lot of electrons.

 

[thepatientmental]

The photoelectric effect is the phenomenon where electrons are emitted from a metal surface when it is struck by light of a certain frequency or above. This effect was studied by Albert Einstein in 1905 and his explanation for it suggested that light has particle-like properties.

Firstly, the photoelectric effect only occurs when the frequency of the light is above a certain threshold. This suggests that light is not just a continuous wave, but is made up of discrete particles, now known as photons. These photons must have enough energy to knock electrons out of the metal surface, and the amount of energy they possess is directly related to their frequency. This is similar to how a billiard ball hitting another can transfer its energy and cause it to move.

Furthermore, the photoelectric effect also follows the law of conservation of energy. This means that the total energy of the incoming photons must be equal to the energy of the emitted electrons. This further supports the particle-like nature of light, as it behaves in a quantized manner, with discrete packets of energy.

To answer your first question, another color of light that can produce the photoelectric effect in potassium is blue light. This is because blue light has a higher frequency than red or orange light, and therefore has more energy to knock electrons out of the metal surface.

Moving on to the second question, the magnetic field lines outside of an isolated bar magnet never cross because magnetic field lines represent the direction and strength of the magnetic field. If they were to cross, it would mean that the magnetic field would have two different directions and strengths at the same point, which is physically impossible.

The double slit experiment using electrons tells us about the wave and particle nature of electrons by demonstrating the phenomenon of wave-particle duality. In this experiment, when electrons are fired through two slits, they behave like waves and produce an interference pattern on the screen behind the slits. This suggests that they have wave-like properties. However, when a detector is placed to observe which slit the electrons pass through, they behave like particles and the interference pattern disappears. This suggests that they also have particle-like properties.

According to classical mechanics, atoms can be at rest. However, in quantum mechanics, the uncertainty principle states that it is impossible to know both the position and momentum of a particle with absolute certainty. This means that atoms can never be at rest, as there is always some uncertainty in their momentum.

The perihelion shift of the planet Mercury is the gradual rotation