OAT Physics: Optics and Waves 4 — Questions and Answers
Question 1: A diverging lens always produces images that are:
- Real, inverted, and reduced
- Virtual, upright, and enlarged
- Virtual, upright, and reduced (Correct answer)
- Real, upright, and reduced
Correct answer: Virtual, upright, and reduced
A diverging (concave) lens always produces virtual, upright, and reduced images regardless of object position.
Question 2: The phenomenon of diffraction is most pronounced when the wavelength of light is:
- Much larger than the aperture
- Much smaller than the aperture
- Comparable to or larger than the aperture (Correct answer)
- Equal to the focal length
Correct answer: Comparable to or larger than the aperture
Diffraction effects are significant when the wavelength is comparable to or larger than the size of the aperture or obstacle.
Question 3: Two sources emit coherent light with wavelength 500 nm. For constructive interference, the path length difference must be:
- An odd multiple of λ/2
- Any integer multiple of λ (Correct answer)
- λ/4
- Zero only
Correct answer: Any integer multiple of λ
Constructive interference requires the path difference Δ = mλ where m = 0, ±1, ±2, … (integer multiples of the wavelength).
Question 4: Which property of light is demonstrated when polarized light passes through a second polarizer oriented at 90°?
- Diffraction
- Interference
- Polarization (extinction) (Correct answer)
- Total internal reflection
Correct answer: Polarization (extinction)
When two polarizers are crossed (90° to each other), no light passes through, demonstrating the transverse polarization of light.
Question 5: A myopic (nearsighted) eye is corrected with a:
- Converging (convex) lens
- Diverging (concave) lens (Correct answer)
- Cylindrical lens
- Plane mirror
Correct answer: Diverging (concave) lens
Myopia is caused by the eye focusing images in front of the retina; a diverging lens diverges rays before they enter the eye, correcting this.
Question 6: The speed of light in a vacuum is approximately:
- 3 × 10⁶ m/s
- 3 × 10⁸ m/s (Correct answer)
- 3 × 10¹⁰ m/s
- 3 × 10⁴ m/s
Correct answer: 3 × 10⁸ m/s
The speed of light in vacuum is c ≈ 3 × 10⁸ m/s (exactly 299,792,458 m/s).
Question 7: A wave has frequency 440 Hz and wavelength 0.75 m. Its speed is:
- 330 m/s (Correct answer)
- 587 m/s
- 293 m/s
- 440 m/s
Correct answer: 330 m/s
Wave speed v = fλ = 440 Hz × 0.75 m = 330 m/s (the speed of sound in air at room temperature).
OAT Physics: Optics and Waves 4
A diverging lens always produces images that are: