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

A sound wave in water travels at 1480 m/s with a wavelength of 0.296 m. Find its frequency f.

λ = 0.296 mv = 1480 m/s

f = kHz

2.Easy

A water wave travels at 0.8 m/s with a wavelength of 0.8 m. Find its frequency f.

λ = 0.8 mv = 0.8 m/s

f = Hz

3.Medium

An object stands 40 cm in front of a thin converging lens with a focal length of 5 cm. Find the image distance d_i. Use the sign convention 1/f = 1/d_o + 1/d_i (f < 0 for a diverging lens, d_i < 0 for a virtual image).

d_o = 40 cmf = 5 cm

d_i = cm

4.Medium

One machine gives a sound level of 72 dB at a certain point. Find the level β at that point when 8 identical machines run at the same time (incoherent sources).

β₁ = 72 dBn = 8

β = dB

5.Hard

A grating with 500 lines per millimetre shows the order-1 maximum of a spectral line at 14.5° from the straight-through direction. Find the wavelength λ of the line.

N = 500 mm⁻¹θ₁ = 14.5°m = 1

λ = nm

6.Hard

A sensor at rest sends ultrasound of 30 kHz towards a car that approaches at 30 m/s and mixes the echo with the emitted signal. Find the beat frequency f_b (speed of sound 343 m/s).

f = 30 kHzu = 30 m/sv = 343 m/s

f_b = Hz

Answer key

1. f = 5 kHz
2. f = 1 Hz
3. d_i = 5.714 cm
4. β = 81.03 dB
5. λ = 500.8 nm
6. f_b = 5751 Hz

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