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
v = 2.21 × 10⁸ m/s

Light travels at 2.21 × 10⁸ m/s in a transparent material. Find its refractive index n.

v = 2.21 × 10⁸ m/sc = 3.00 × 10⁸ m/s
n =
2.Easy
PI = 4 × 10⁻⁸ W/m²

The sound intensity near a quiet library is 4 × 10⁻⁸ W/m². Find the sound intensity level β in decibels.

I = 4 × 10⁻⁸ W/m²I0 = 10⁻¹² W/m²
β = dB
3.Medium
95 dB?1 m5 m

A small source sends sound equally in all directions. The level is 95 dB at 1 m from it. Find the level β2 at 5 m, ignoring absorption and reflections.

β1 = 95 dBr1 = 1 mr2 = 5 m
β2 = dB
4.Medium
P5 × 70 dB

One machine gives a sound level of 70 dB at a certain point. Find the level β at that point when 5 identical machines run at the same time (incoherent sources).

β1 = 70 dBn = 5
β = dB
5.Hard
Fdo​ = 25 cmR = 20 cm

An object is 25 cm in front of a concave mirror with a radius of curvature of 20 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 = 20 cm
di = cm
6.Hard
λ = 450 nmθ2​ = ?

Light of wavelength 450 nm falls at right angles on a grating with 600 lines per millimetre. Find the angle θ2 of the order-2 maximum.

N = 600 mm⁻¹λ = 450 nmm = 2
θ2 = °

Answer key

  1. 1. n = 1.357
  2. 2. β = 46.02 dB
  3. 3. β2 = 81.02 dB
  4. 4. β = 76.99 dB
  5. 5. di = 16.67 cm
  6. 6. θ2 = 32.68 °

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