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 = 0.686 mv = ?f = 500 Hz

A sound wave in air has a frequency of 500 Hz and a wavelength of 0.686 m. Find its speed v.

f = 500 Hzλ = 0.686 m
v = m/s
2.Easy
PI = 6 × 10⁻³ W/m²

The sound intensity near a lawn mower is 6 × 10⁻³ W/m². Find the sound intensity level β in decibels.

I = 6 × 10⁻³ W/m²I0 = 10⁻¹² W/m²
β = dB
3.Medium
θc = ?90°diamond, n1​ = 2.42glycerol, n2​ = 1.47

Light travels in diamond (n = 2.42) towards a flat boundary with glycerol (n = 1.47). Find the critical angle θc beyond which it is totally reflected.

n1 = 2.42n2 = 1.47
θc = °
4.Medium
L = 1.5 mn = 4

A pipe open at both ends is 1.5 m long. The speed of sound is 343 m/s. Find the frequency f4 of its harmonic number 4.

v = 343 m/sn = 4L = 1.5 m
f4 = Hz
5.Hard
f1​ = 20 cmf2​ = 5 cm15 cm50 cm

Two thin lenses share an axis, 50 cm apart: lens 1 with f₁ = 20 cm and lens 2 with f₂ = 5 cm. An object stands 15 cm in front of lens 1. Find the position di2 of the final image measured from lens 2 (positive beyond lens 2, real-is-positive convention).

f1 = 20 cmf2 = 5 cms = 50 cmdo = 15 cm
di2 = cm
6.Hard
Fdo​ = 25 cmR = 16 cm

An object is 25 cm in front of a convex mirror with a radius of curvature of 16 cm. Find the image distance di, positive for an image in front of the mirror (real) and negative for one behind it (virtual).

do = 25 cmR = 16 cm
di = cm

Answer key

  1. 1. v = 343 m/s
  2. 2. β = 97.78 dB
  3. 3. θc = 37.4 °
  4. 4. f4 = 457.3 Hz
  5. 5. di2 = 5.238 cm
  6. 6. di = −6.061 cm

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