4.2 What Is A Wave?

Question 1

What is a wave?

Answer 1

Propagation of a disturbance through a medium.

Question 2

What happens as a wave travels through the medium?

Answer 2

Molecules of the medium are displaced from equilibrium positions, made to oscillate about these positions in simple harmonic motion.

Question 3

What can a wave transfer?

Answer 3

Energy and momentum.

Question 4

What are some examples of mechanical waves?

Answer 4

Water waves, sound, earthquake waves.

Question 5

What medium do mechanical waves travel through?

Answer 5

Require a physical medium, cannot propagate in vacuum.

Question 6

What is the wave speed determined by for mechanical waves?

Answer 6

Determined by the properties of the medium.

Question 7

What is the disturbance of particles in mechanical waves?

Answer 7

Change of a property of the medium from its equilibrium value - when there is no waves.

Question 8

What are some example of electromagnetic waves?

Answer 8

Light, radio waves, X rays, infrared radiation, ultraviolet radiation.

Question 9

What medium do electromagnetic waves travel through?

Answer 9

Can propagate in a vacuum as well as various physical media.

Question 10

What is the wave speed determined by for electromagnetic waves?

Answer 10

In vacuum all waves travel at 3x10^8 ms^-1

Question 11

What is the disturbance of particles in electromagnetic waves?

Answer 11

The oscillating values of electric and magnetic fields.

Question 12

What is displacement?

Answer 12

Vector to the position of a point in a medium from the equilibrium position of the point.

Question 13

What is amplitude?

Answer 13

Maximum displacement.

Question 14

What is a crest?

Answer 14

Maximum positive displacement.

Question 15

What is a trough?

Answer 15

Maximum negative displacement.

Question 16

What is wavelength?

Answer 16

Length of a full wave. May be found from a displacement versus distance graph.

Question 17

What is frequency?

Answer 17

Number of full waves produced by a source in 1 second - in Hz. Frequency is inverse of period f = 1/T

Question 18

What is period?

Answer 18

Time taken fro one full wave to pass by. May be found from a displacement versus time graph. Period is inverse of frequency T = 1/f

Question 19

What is wave speed?

Answer 19

Speed at which a crest moves past an observer at rest in the medium. v = f x lambda

Question 20

What is intensity?

Answer 20

Power transferred per unit area by a wave. Proportional to the square of the amplitude. For a point source emitting uniformly in all direction, intensity a distance d from point source has intensity proportional to 1/d^2.

Question 21

What is a transverse wave?

Answer 21

Displacement of medium is perpendicular to direction of wave movement or energy transfer.

Question 22

What is a longitudinal wave?

Answer 22

Displacement of medium is parallel to direction of wave momentum or energy transfer.

Question 23

What is a ray?

Answer 23

Lines indicating the direction of energy transfer of a wave.

Question 24

What is a wavefront?

Answer 24

Surface at right angles to rays. All points on a wavefront have the same phase.