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
PI = 4 × 10⁻³ W/m²

The sound intensity near a lawn mower is 4 × 10⁻³ W/m². Find the sound intensity level β in decibels.

I = 4 × 10⁻³ W/m²I0 = 10⁻¹² W/m²
β = dB
2.Easy
λ = 0.8 mv = ?f = 1 Hz

A water wave has a frequency of 1 Hz and a wavelength of 0.8 m. Find its speed v.

f = 1 Hzλ = 0.8 m
v = m/s
3.Medium
FFdo​ = 8 cmf = 20 cm

An object stands 8 cm in front of a thin converging lens with a focal length of 20 cm. Find the image distance di. Use the sign convention 1/f = 1/do + 1/di (f < 0 for a diverging lens, di < 0 for a virtual image).

do = 8 cmf = 20 cm
di = cm
4.Medium
48.8°90°n1​ = ?glycerol, n2​ = 1.47

Light inside a transparent block is totally reflected at the boundary with glycerol (n = 1.47) for every angle of incidence above 48.8°. Find the refractive index n1 of the block.

θc = 48.8°n2 = 1.47
n1 =
5.Hard
λ = 650 nma = 0.08 mm

Light of wavelength 650 nm passes through a single slit 0.08 mm wide. Find the angle θ2 of dark fringe number 2 from the straight-through direction.

λ = 650 nma = 0.08 mmm = 2
θ2 = °
6.Hard
SO10 m/sf = 40 kHz

A parking sensor at rest sends ultrasound of 40 kHz towards a car that approaches at 10 m/s. Find the frequency f″ of the echo received back at the sensor (speed of sound 343 m/s).

f = 40 kHzu = 10 m/sv = 343 m/s
f″ = Hz

Answer key

  1. 1. β = 96.02 dB
  2. 2. v = 0.8 m/s
  3. 3. di = −13.33 cm
  4. 4. n1 = 1.954
  5. 5. θ2 = 0.9311 °
  6. 6. f″ = 42402 Hz

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