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 = 5.781 mv = ?f = 256 Hz

A sound wave in water has a frequency of 256 Hz and a wavelength of 5.781 m. Find its speed v.

f = 256 Hzλ = 5.781 m
v = m/s
2.Easy
PI = 2 × 10⁻⁴ W/m²

The sound intensity near a lawn mower is 2 × 10⁻⁴ W/m². Find the sound intensity level β in decibels.

I = 2 × 10⁻⁴ W/m²I0 = 10⁻¹² W/m²
β = dB
3.Medium
L = 0.75 mn = 3

A string fixed at both ends is 0.75 m long; waves travel on it at 300 m/s. Find the frequency f3 of its harmonic number 3.

v = 300 m/sn = 3L = 0.75 m
f3 = Hz
4.Medium
FFdo​ = 50 cmf = 15 cm

An object stands 50 cm in front of a thin converging lens with a focal length of 15 cm. Find the magnification m (negative for an inverted image).

do = 50 cmf = 15 cm
m =
5.Hard
λ = 600 nmd = 0.5 mmL = 1.5 m

Light of wavelength 600 nm falls on two slits 0.5 mm apart. The screen is 1.5 m away. Find the spacing Δy between neighbouring bright fringes.

λ = 600 nmd = 0.5 mmL = 1.5 m
Δy = mm
6.Hard
λ = 500 nmθ3​ = ?

Light of wavelength 500 nm falls at right angles on a grating with 200 lines per millimetre. Find the angle θ3 of the order-3 maximum.

N = 200 mm⁻¹λ = 500 nmm = 3
θ3 = °

Answer key

  1. 1. v = 1480 m/s
  2. 2. β = 83.01 dB
  3. 3. f3 = 600 Hz
  4. 4. m = −0.4286
  5. 5. Δy = 1.8 mm
  6. 6. θ3 = 17.46 °

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