8 original questions from New Regents. The worksheet, answer key, and browser practice are free.
Ultraviolet Light and Molecular Change 4 questions
Ultraviolet Light and Molecular Change
New Regents original practice • Name: ____________________ Date: __________ Show your work for written answers.
In this worksheet’s model, a molecule can undergo a change when it absorbs one photon whose energy meets a stated threshold.
Question 1
Which statement applies to the model when every photon has energy below the threshold?
- Each individual photon falls short of the threshold.
- Increasing the number of photons makes each photon more energetic.
- Any photon can drive the change regardless of its energy.
- Photon energy equals the number of molecules.
Question 2
Explain why a shorter wavelength corresponds to more energy per photon in a vacuum.
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Question 3
Which has the higher frequency according to the electromagnetic spectrum in the 2025 tables?
- Ultraviolet light
- Infrared light
- They have identical frequencies.
- The spectrum cannot compare them.
Question 4
Two sources have the same wavelength but different numbers of photons per second. Explain which feature changes and which remains fixed.
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A Model Molecular Change 4 questions
A Model Molecular Change
Use the information below to answer the questions.
A modeled molecule changes only when it absorbs a photon with at least 5.00 × 10-19 J. The table gives the wavelength and energy per photon of three sources.
| Source | Wavelength (nm) | Energy per photon (× 10-19 J) |
|---|---|---|
| P | 300 | 6.62 |
| Q | 400 | 4.97 |
| R | 600 | 3.31 |
Question 5
Which source supplies photons with enough energy to meet the model threshold?
- P only
- Q only
- P and Q
- All three
Question 6
Calculate how far below the threshold a photon from Q is. Include units.
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Question 7
Which comparison describes P relative to R?
- P has shorter wavelength and higher energy per photon.
- P has longer wavelength and higher energy per photon.
- P has shorter wavelength and lower energy per photon.
- They have equal wavelengths and energies.
Question 8
A student says a higher intensity of source R guarantees that every photon will meet the threshold. Use the table and the model to evaluate the claim.
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