When a beam of light shines on a metal surface, there is the possibility that el
ID: 1445272 • Letter: W
Question
When a beam of light shines on a metal surface, there is the possibility that electrons may be released from the surface of the metal. These electrons are usually called photoelectrons. The maximum kinetic energy of the photoelectrons are given by the following equation: KEmax = h f - W where h is Plancks' constant, f is the frequency of the light, and W is the workfunction of the metal surface. A scientist is performing a series of measurement using different colors of light as well as different metal surfaces.
19. The scientist measures the relationship between the maximum kinetic energy of the photoelectrons and the frequency of the light for three different surfaces, A, B, and C. Which of the following graphs would best represent her findings?
20. A metal surface is illuminated with violet light and electrons are ejected at a given rate with a certain maximum kinetic energy. If the intensity of the light is increased, electrons are ejected ____
A) at higher rate, but with a reduced maximum kinetic energy
B) at higher rate and with no change in their maximum kinetic energy
C) at higher rate and with higher maximum kinetic energy
D) at the same rate, but with higher maximum kinetic energy
A B C A B Frequency Frequency A B C A B c Frequency Frequency 20.Explanation / Answer
19. The scientist measures the relationship between the maximum kinetic energy of the photoelectrons and the frequency of the light for three different surfaces, A, B, and C. Which of the following graphs would best represent her findings?
ans: Graph A because hf-w, for different metals are different but all >0, so x intercept should be positive, they all have same slope h, thus are parallel lines
20. A metal surface is illuminated with violet light and electrons are ejected at a given rate with a certain maximum kinetic energy. If the intensity of the light is increased, electrons are ejected
ans: B) at higher rate and with no change in their maximum kinetic energy because hf-w, for each photon there are the same passibility to generator a photonelectron, thus more photon means more electrons and large intensity, but kem only depends on f, not intensity
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