Regents Physics 5 — Questions and Answers
Question 1: A photon has a frequency of 6.0 × 10¹⁴ Hz. What is its energy? (h = 6.63 × 10⁻³⁴ J·s)
- 1.1 × 10⁻⁴⁸ J
- 3.98 × 10⁻¹⁹ J (Correct answer)
- 9.1 × 10⁻⁴⁸ J
- 1.1 × 10⁻¹⁹ J
Correct answer: 3.98 × 10⁻¹⁹ J
E = hf = (6.63 × 10⁻³⁴)(6.0 × 10¹⁴) ≈ 3.98 × 10⁻¹⁹ J.
Question 2: A spring with spring constant k = 200 N/m is compressed 0.05 m. What is the elastic potential energy stored?
- 0.25 J (Correct answer)
- 5 J
- 10 J
- 0.5 J
Correct answer: 0.25 J
PE = ½kx² = ½(200)(0.05)² = ½(200)(0.0025) = 0.25 J.
Question 3: In the photoelectric effect, increasing the intensity of incident light (at constant frequency) causes:
- Electrons to be emitted with greater kinetic energy
- More electrons to be emitted per second (Correct answer)
- Electrons to have a higher threshold frequency
- No electrons to be emitted
Correct answer: More electrons to be emitted per second
Greater intensity means more photons per second, each ejecting one electron, so the emission rate increases but individual electron energy does not.
Question 4: Two resistors of 6 Ω each are connected in parallel. What is the equivalent resistance?
- 12 Ω
- 6 Ω
- 3 Ω (Correct answer)
- 1 Ω
Correct answer: 3 Ω
For two equal resistors in parallel: R_eq = R/2 = 6/2 = 3 Ω.
Question 5: A standing wave is formed on a string. The distance between two adjacent nodes is 0.4 m. What is the wavelength?
- 0.2 m
- 0.4 m
- 0.8 m (Correct answer)
- 1.6 m
Correct answer: 0.8 m
Adjacent nodes are separated by half a wavelength, so λ = 2 × 0.4 = 0.8 m.
Question 6: Which of the following describes the Doppler effect?
- The bending of waves around obstacles
- The change in observed frequency due to relative motion between source and observer (Correct answer)
- The interference of two waves producing a standing wave
- The increase in wave speed as it enters a denser medium
Correct answer: The change in observed frequency due to relative motion between source and observer
The Doppler effect is the apparent change in frequency when source and observer are moving relative to each other.
Question 7: A nucleus of carbon-14 undergoes beta-minus decay. The resulting nucleus is:
- Boron-14
- Nitrogen-14 (Correct answer)
- Carbon-13
- Oxygen-14
Correct answer: Nitrogen-14
In beta-minus decay, a neutron converts to a proton, increasing the atomic number by 1: carbon (Z=6) becomes nitrogen (Z=7), mass number unchanged at 14.
Regents Physics 5
A photon has a frequency of 6.0 × 10¹⁴ Hz.
What is its energy? (h = 6.63 × 10⁻³⁴ J·s)