NSAA NSAA Physics - Waves and Optics 1 — Questions and Answers
Question 1: A wave has a frequency of 5 Hz and a wavelength of 4 m. What is its speed?
- 1.25 m/s
- 9 m/s
- 20 m/s (Correct answer)
- 40 m/s
Correct answer: 20 m/s
Wave speed v = fλ = 5 × 4 = 20 m/s.
Question 2: Which type of wave requires a medium to travel through?
- Electromagnetic waves
- Light waves
- Mechanical waves (Correct answer)
- Radio waves
Correct answer: Mechanical waves
Mechanical waves, such as sound, require a physical medium to propagate.
Question 3: A light ray passes from air into glass and bends toward the normal. This is because in glass the light:
- Has higher frequency
- Travels faster
- Travels slower (Correct answer)
- Has longer wavelength
Correct answer: Travels slower
Light slows down when entering a denser medium, causing refraction toward the normal.
Question 4: What is the period of a wave with frequency 50 Hz?
- 0.002 s
- 0.02 s (Correct answer)
- 0.2 s
- 50 s
Correct answer: 0.02 s
Period T = 1/f = 1/50 = 0.02 s.
Question 5: In the double-slit experiment, constructive interference occurs when the path difference between the two sources is:
- An odd multiple of λ/2
- Any multiple of λ (Correct answer)
- Zero only
- A non-integer multiple of λ
Correct answer: Any multiple of λ
Constructive interference occurs when path difference = nλ (n = 0, 1, 2, ...), so waves arrive in phase.
Question 6: A concave mirror has a focal length of 10 cm. An object is placed 30 cm in front of it. Where is the image formed?
- 10 cm behind the mirror
- 15 cm in front of the mirror (Correct answer)
- 30 cm in front of the mirror
- 20 cm in front of the mirror
Correct answer: 15 cm in front of the mirror
1/f = 1/v + 1/u → 1/10 = 1/v + 1/30 → 1/v = 3/30 - 1/30 = 2/30, so v = 15 cm in front.
NSAA NSAA Physics - Waves and Optics 1
A wave has a frequency of 5 Hz and a wavelength of 4 m.
What is its speed?