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 = 3.43 mv = ?f = 100 Hz

A sound wave in air has a frequency of 100 Hz and a wavelength of 3.43 m. Find its speed v.

f = 100 Hzλ = 3.43 m
v = m/s
2.Easy
v = 1.24 × 10⁸ m/s

Light travels at 1.24 × 10⁸ m/s in a transparent material. Find its refractive index n.

v = 1.24 × 10⁸ m/sc = 3.00 × 10⁸ m/s
n =
3.Medium
35°90°n1​ = ?ethanol, n2​ = 1.36

Light inside a transparent block is totally reflected at the boundary with ethanol (n = 1.36) for every angle of incidence above 35°. Find the refractive index n1 of the block.

θc = 35°n2 = 1.36
n1 =
4.Medium
L = 1.2 mn = 1

A pipe closed at one end is 1.2 m long. The speed of sound is 343 m/s. Find the frequency f1 of its fundamental (first harmonic).

v = 343 m/sn = 1L = 1.2 m
f1 = Hz
5.Hard
λ = 532 nmd = 0.5 mmL = 2 m

Light of wavelength 532 nm falls on two slits 0.5 mm apart. The screen is 2 m away. Find the spacing Δy between neighbouring bright fringes.

λ = 532 nmd = 0.5 mmL = 2 m
Δy = mm
6.Hard
f1​ = 20 cmf2​ = 20 cm15 cm15 cm

Two thin lenses share an axis, 15 cm apart: lens 1 with f₁ = 20 cm and lens 2 with f₂ = 20 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 = 20 cms = 15 cmdo = 15 cm
di2 = cm

Answer key

  1. 1. v = 343 m/s
  2. 2. n = 2.419
  3. 3. n1 = 2.371
  4. 4. f1 = 71.46 Hz
  5. 5. Δy = 2.128 mm
  6. 6. di2 = 27.27 cm

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