Module 3

Question 1

What increases the speed of sound in ocean? (3)

Answer 1

Temperature 1C = 4.0m/s
Salinity 1 practical salinity unit = 1.4m/s
Pressure (at depth 100m) = 1.7m/s

Question 2

What is the inverse square law?

Answer 2

intensity of sound or light is inversely proportional to the square of the distance from the source

Question 3

Does v, f, or ƛ of reflected wave change?

Answer 3

NO

Question 4

what happens when a wave travels in one medium and crosses into a second medium where its velocity is different?

Answer 4

the direction of the wave changes

Question 5

If v2 > v1 then

Answer 5

angle2 > angle1

Question 6

If V2 > V1, which way the wave will refract?

Answer 6

Away from the normal

Question 7

How are standing waves formed?

Answer 7

due to superposition of two waves of same A-amplitude, f-frequency and ƛ- wavelength traveling in opposite directions in the same medium

Question 8

Why are these waves called standing waves?

Answer 8

Because it doesn’t appear to be travelling. The cord appears to have segments that oscillate up and down in a fixed pattern

Question 9

What are natural or resonant frequencies?

Answer 9

For certain frequencies, standing waves are formed in the string.

Question 10

Shorter the length, the lower or higher the frequency?

Answer 10

Higher frequency

Question 11

How can waves be interfered?

Answer 11

superposition of two traveling waves in the same medium

Question 12

What are beats?

Answer 12

When two sound waves of slightly different frequencies f1 and f2 superimpose the loudness of the resulting sound rises and falls periodically.

Question 13

What happens when a tuning fork is loaded with a drop of wax?

Answer 13

the frequency drops

Question 14

What is pitch determined by?

Answer 14

frequency of sound

Question 15

What is loudness determined by?

Answer 15

the intensity of sound

Question 16

What is the intensity of sound?

Answer 16

energy transported by a wave per second across a unit area held perpendicular to the energy flow

Question 17

What is loudness measured by?

Answer 17

the intensity level (also called the sound level)

Question 18

What happens to the intensity level when you double or halve the intensity by a factor of 2?

Answer 18

halving the intensity by a factor of 2, decreases the Intensity level by 3dB

Question 19

What happens to the intensity level when you increase or decrease the intensity by a factor of 10?

Answer 19

it increases the intensity level by 10dB and also doubles the loudness

Question 20

What will give simple harmonic motion?

Answer 20

a restoring force that is directly proportional to -x therefore the force is a negative constant times a displacement.

Question 21

What happens to the energy of the system when you stretched a spring twice as far to x=24?

Answer 21

the total energy is proportional to the square of the amplitude A, so stretching it twice as far quadruples the energy (2^2=4). The force you exert is proportional to the displacement x.

Question 22

What happens to the maximum velocity of the oscillating mass when you stretched a spring twice as far to x=24?

Answer 22

when the amplitude is doubled the maximum velocity must be doubled

Question 23

What happens to the maximum acceleration of the mass when you stretched a spring twice as far to x=24?

Answer 23

since the force is twice as great when we stretch the spring twice as far (F = kx), the acceleration is also twice as great: a∝ F∝ x

Question 24

An electric charge q moving in an electric field E can be decelerated to a stop if the force F = qE acts in the direction opposite to the cahrge’s velocity? Can a magnetic field be used to stop a charge particle?

Answer 24

No, because the force is always perpendicular to the velocity of the particle and thus can only change the direction but not the magnitude of its velocity. Also magnetic force cannot do work on the particle (force and displacement are perpendicular) and so cannot change the K.E of the particle

Question 25

What is the path of charged particle in a uniform magnetic field if its velocity is not perpendicular to the magnetic field?

Answer 25

the velocity vector can be broken down into components parallel and perpendicular to the field. The velocity component parallel to the field lines experience no force (angle = 0) so this component remains constant. Velocity component perpendicular to the field results in circular motions about the field lines. Putting these two motions together produces a helical motion around the field lines.