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
Pβ = 65 dB

The sound intensity level at a point is 65 dB. Find the sound intensity I.

β = 65 dBI0 = 10⁻¹² W/m²
I = µW/m²
2.Easy
PI = 1 × 10⁻⁴ W/m²

The sound intensity near a lawn mower is 1 × 10⁻⁴ W/m². Find the sound intensity level β in decibels.

I = 1 × 10⁻⁴ W/m²I0 = 10⁻¹² W/m²
β = dB
3.Medium
L = ?n = 4

A pipe open at both ends must have its harmonic number 4 at 858 Hz. The speed of sound is 343 m/s. Find the length L of the pipe.

v = 343 m/sn = 4f4 = 858 Hz
L = m
4.Medium
S10 m/sOf = 1200 Hz

A source of 1200 Hz moves at 10 m/s towards a stationary observer. The speed of sound is 343 m/s. Find the frequency f′ that the observer hears.

f = 1200 Hzv = 343 m/svs = 10 m/s
f′ = Hz
5.Hard
λ = 650 nmd = 0.4 mmL = 1.5 my = ?

Light of wavelength 650 nm falls on two slits 0.4 mm apart. The screen is 1.5 m away. Find the distance y2 from the central bright fringe to bright fringe number 2.

λ = 650 nmd = 0.4 mmL = 1.5 mm = 2
y2 = mm
6.Hard
λ = 486 nmθ3​ = ?

Light of wavelength 486 nm falls at right angles on a grating with 600 lines per millimetre. Find the angle θ3 of the order-3 maximum.

N = 600 mm⁻¹λ = 486 nmm = 3
θ3 = °

Answer key

  1. 1. I = 3.162 µW/m²
  2. 2. β = 80 dB
  3. 3. L = 0.7995 m
  4. 4. f′ = 1236 Hz
  5. 5. y2 = 4.875 mm
  6. 6. θ3 = 61.02 °

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