Waves, sound & optics worksheet with answers

Free printable Waves, sound & optics worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
λ = 0.0686 mv = 343 m/sf = ?

A sound wave in air travels at 343 m/s with a wavelength of 0.0686 m. Find its frequency f.

λ = 0.0686 mv = 343 m/s
f = kHz
2.Easy
v = ?

Find the speed v of light in diamond, which has a refractive index of 2.42.

n = 2.42c = 3.00 × 10⁸ m/s
v = m/s
3.Medium
85 dB?2 m20 m

A small source sends sound equally in all directions. The level is 85 dB at 2 m from it. Find the level β2 at 20 m, ignoring absorption and reflections.

β1 = 85 dBr1 = 2 mr2 = 20 m
β2 = dB
4.Medium
θc = ?90°glycerol, n1​ = 1.47ethanol, n2​ = 1.36

Light travels in glycerol (n = 1.47) towards a flat boundary with ethanol (n = 1.36). Find the critical angle θc beyond which it is totally reflected.

n1 = 1.47n2 = 1.36
θc = °
5.Hard
SO15 m/sf = 40 kHz

A sensor at rest sends ultrasound of 40 kHz towards a car that approaches at 15 m/s and mixes the echo with the emitted signal. Find the beat frequency fb (speed of sound 343 m/s).

f = 40 kHzu = 15 m/sv = 343 m/s
fb = Hz
6.Hard
λ = 450 nmd = 0.1 mmL = 1 my = ?

Light of wavelength 450 nm falls on two slits 0.1 mm apart. The screen is 1 m away. Find the distance y3 from the central bright fringe to bright fringe number 3.

λ = 450 nmd = 0.1 mmL = 1 mm = 3
y3 = mm

Answer key

  1. 1. f = 5 kHz
  2. 2. v = 1.24 × 10⁸ m/s
  3. 3. β2 = 65 dB
  4. 4. θc = 67.69 °
  5. 5. fb = 3659 Hz
  6. 6. y3 = 13.5 mm

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