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
L = 0.8 m

A string of length 0.8 m and mass 15 g is stretched with a tension of 50 N. Find the speed v of transverse waves on it.

L = 0.8 mm = 15 gT = 50 N
v = m/s
2.Easy
L = 1.5 m

A string of length 1.5 m and mass 20 g is stretched with a tension of 100 N. Find the speed v of transverse waves on it.

L = 1.5 mm = 20 gT = 100 N
v = m/s
3.Medium
FFdo​ = 60 cmf = 8 cm

An object stands 60 cm in front of a thin converging lens with a focal length of 8 cm. Find the magnification m (negative for an inverted image).

do = 60 cmf = 8 cm
m =
4.Medium
85 dB?5 m50 m

A small source sends sound equally in all directions. The level is 85 dB at 5 m from it. Find the level β2 at 50 m, ignoring absorption and reflections.

β1 = 85 dBr1 = 5 mr2 = 50 m
β2 = dB
5.Hard
λ = ?d = 0.1 mmL = 1.5 m18 mm

Two slits 0.1 mm apart are lit with monochromatic light. On a screen 1.5 m away, bright fringe number 2 lies 18 mm from the central fringe. Find the wavelength λ.

d = 0.1 mmL = 1.5 my2 = 18 mmm = 2
λ = nm
6.Hard
θa​ = ?n1​ = 1.52n2​ = 1.5n0​ = 1.00

An optical fibre has a core with n₁ = 1.52 and a cladding with n₂ = 1.5. Find the largest angle θa to the fibre axis at which light from air can enter the end of the fibre and still be guided by total internal reflection.

n1 = 1.52n2 = 1.5n0 = 1.00
θa = °

Answer key

  1. 1. v = 51.64 m/s
  2. 2. v = 86.6 m/s
  3. 3. m = −0.1538
  4. 4. β2 = 65 dB
  5. 5. λ = 600 nm
  6. 6. θa = 14.23 °

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