Question 29·Medium·Rhetorical Synthesis
While preparing a presentation, a student gathers the following notes about the photoelectric effect:
- Electrons are ejected from a metal surface only when the light striking it has a frequency above a certain threshold.
- Increasing the intensity (brightness) of the light raises the number of electrons emitted but does not make them move faster.
- Raising the light’s frequency above the threshold boosts the kinetic energy of the emitted electrons.
- Albert Einstein explained the effect in 1905 by proposing that light consists of quantized packets called photons.
The student wants to emphasize the relationship between light frequency and the kinetic energy of the ejected electrons. Which choice most effectively uses relevant information from the notes to accomplish this goal?
For rhetorical synthesis questions like this, first restate the goal in your own words (what exactly does the sentence need to emphasize?). Then scan the notes for the detail that directly addresses that goal, especially looking for matching keywords (here, “frequency” and “kinetic energy”). Finally, choose the answer choice that most directly and specifically restates or combines that relevant note, and eliminate any choices that are true but focus on different aspects (like definitions, history, or related but not requested variables such as intensity).
Hints
Focus on what the question is really asking
Underline the key ideas in the question: light frequency and kinetic energy of the ejected electrons. Which answer choice talks about both of these?
Use the notes as your guide
Look through the bullet-point notes and find the one that discusses how changing the light’s frequency affects how energetically the electrons are emitted.
Eliminate irrelevant but true statements
Some choices will correctly describe the photoelectric effect but not mention the specific relationship the student wants to emphasize. Cross out any answer that talks about intensity, basic definition, or history instead of the link between frequency and kinetic energy.
Step-by-step Explanation
Identify the goal in the question
The prompt says: “The student wants to emphasize the relationship between light frequency and the kinetic energy of the ejected electrons.”
So the correct answer must clearly connect frequency of the light with kinetic energy (how fast/energetic) the electrons are.
Find the matching note(s)
Look back at the notes for anything that mentions both frequency and kinetic energy:
- One note says: “Electrons are ejected from a metal surface only when the light striking it has a frequency above a certain threshold.” (frequency and threshold)
- Another says: “Raising the light’s frequency above the threshold boosts the kinetic energy of the emitted electrons.” (this one directly states how frequency affects kinetic energy).
This second note is the key idea the student wants to emphasize.
Check each choice against the goal
Now compare each answer choice to the goal:
- Choice A talks about electrons being emitted from a metal surface, but says nothing about frequency or kinetic energy.
- Choice B talks about intensity (brightness) and the number of electrons, not frequency or kinetic energy.
- Choice C gives a historical detail about Einstein and photons, not the relationship the question asks about.
- Only one choice directly connects frequency with the kinetic energy of the electrons, as in the key note from Step 2.
Choose the sentence that directly states the relationship
Because we need a sentence that clearly shows how increasing the light’s frequency (above a threshold) changes the kinetic energy of ejected electrons, the best choice is:
D) When the frequency of the light exceeds the threshold, the kinetic energy of the ejected electrons increases.