Teaching Physics with the Physics Suite

Edward F. Redish

Home | Action Research Kit| Sample Problems | Resources | Product Information

Problems Sorted by Type | Problems Sorted by Subject | Problems Sorted by Chapter in UP

Hearing and seeing around a corner

We can make the observation that we can hear around corners (somewhat) but not see around corners. Estimate why this is so by considering a doorway and two kinds of waves passing through it.

  1. A beam of red light (λ = 660 nm)

  2. A sound wave playing an "A" (f = 440 Hz).

Treat these two waves as plane waves passing through a slit whose width equals the width of the door. Find the angle that gives the position of the first dark diffraction fringe. From that, assuming you are 2 m back from the door, estimate how far outside the door you could be and still detect the wave. (See the picture for a clarification. The distance x is desired.)

Note: The speed of light in air is about 3 x 108 m/s and the speed of sound in air is about 330 m/s.

Not finding what you wanted? Check the Site Map for more information.

Page last modified October 31, 2002: OP16