Question

Questions 2. [1] Wavefronts represent all points of the wave cycle. This statement is: correct, incorrect. [2] Wavefronts are: the forward sides of a wave, the backward sides of a wave, wavelengths, geometric shapes, points of both maximum and minimum values. [3] Sound propagates through the air. Wavefronts are drawn to show where the air undergoes a maximum compression. Halfway between two successive wavefronts, the air: undergoes a maximum compression returns to normal, undergoes a maximum expansion, somewhere between a maximum compression and a maximum expansion, undetermined. [4] Sound is: continually emitted by the source, emitted only when a wavefront is emitted, emitted only between the emissions of wavefronts, emitted periodically but not related to wavefronts, emitted all at once. [5] Sound is emitted from a stationary source. The sound is heard by an observer with no change in medium. The wavefronts are: closer together in the direction of the observer, equally spaced everywhere, closer together in the direction opposite of the observer, alternating between moving closer together and father apart, undetermined. [6] Sound is emitted from a stationary source. The sound is heard by an observer with no change in medium. The wavefronts move: faster in the direction of the observer, equally fast everywhere, faster in the direction opposite of the observer, alternating between moving faster and slower, undetermined e [7] The distance between two successive wavefronts is 19 mm. The wavelength is: less than 19 mm, equal to 19 mm, greater than 19 mm, undetermined. [8] Sound is created from a source with a period of 21 s. The source emits a wavefront. The time before the source emits the next wavefront is: greater than 21 seconds, equal to 21 seconds, less than 21 seconds, undetermined. [9] 10 wavefronts pass by an observer each second. The frequency observed is: less than 10 Hz, equal to 10 Hz, greater than 10 Hz, undetermined. [10] If a given wavefront is a vertical line, then a possible propagation direction is: up or right 27

Answer 1

Ans.4) Sound is continually emitted by the source.

Ans.5) Since the source is stationary and there is no change in the medium, the wavefronts are equally spaced everywhere.

Ans.6) Speed of sound is independent of the motion of the source. It depends only on the medium. As the medium does not change, hence the wavefronts move equally fast. Speed of wavefronts equals speed of sound.

Ans.7) Wavelength equals the distance between two successive wavefronts. So the wavelength is 19mm.

Ans.8) Time between the emission of two successive wavefronts equals the period of the wave. So the time before the source emits the next wavefront is 21 seconds.

Ans.9) Frequency equals numbers of wavefronts passing a given point each second. So the frequency observed is 10 Hz.

Ans.10) Direction of propagation is always perpendicular to the wavefront. As the given wavefront is a verticle line, hence the possible direction of propagation is towards right.