9-11 ODDS

Question 1

Does the medium in which a wave travels move with the wave?

Answer 1

No; the propagation of energy travels, not the medium itself.

Question 2

What effect does Earth’s magnetic field have on the intensity of cosmic rays striking Earth’s surface?

Answer 2

Earth’s magnetic field deflects many of the incoming cosmic rays, reducing the intensity of rays striking Earth’s surface.

Question 2

How do the speed of a wave source and the speed of the waves themselves compare when a wave barrier is being produced? How do they compare when a bow wave is being produced?

Answer 2

The speed of the waves and the speed of the source are the same when a wave barrier is produced. Wave speed is greater when a bow is produced.

Question 2

True or False: A sonic boom occurs only when an aircraft is breaking through the sound barrier.

Answer 2

False, because a sonic boom occurs for an aircraft moving faster than the speed of sound.

Question 2

In what sense does the law of reflection hold for a diffuse reflector?

Answer 2

The law of reflection holds locally at each tiny part of the irregular surface, but not for the diffuse surface as a whole.

Question 3

How are frequency and period related?

Answer 3

Frequency and period are inverses of each other.

Question 3

What is the law of reflection for sound?

Answer 3

The angle of incidence is equal to the angle of reflection.

Question 4

Does sound travel faster in warm air or in cold air?

Answer 4

Sound travels faster in warm air because the air molecules in warm air themselves travel faster and therefore don’t take as long before they bump into one another. A shorter time for the molecules to bump against one another results in a faster speed of sound.

Question 5

How is the strength of a magnetic field in a coil affected when a piece of iron is placed inside?

Answer 5

A piece of iron strengthens the electromagnet because the alignment of domains in the piece of iron adds to the overall field.

Question 6

Distinguish between forced vibrations and resonance.

Answer 6

Forced vibrations occur when a surface is forced to vibrate. Resonance occurs when the forcing frequency matches the natural frequency of the surface.

Question 7

How does the frequency of induced voltage compared with how frequently a magnet is plunged into and out of a coil of wire?

Answer 7

Both frequencies are the SAME.

Question 8

Distinguish between constructive interference and destructive interference.

Answer 8

Constructive Interference- Increased wave amplitude

Destructive Interference- Reduced wave amplitude

Question 9

What happens when:

The energy in infrared light is incident on glass?

Answer 9

The energy in infrared light becomes thermal energy.

Question 11

What is the color of the peak frequency of solar radiation? To what color of light are our eyes most sensitive?

Answer 11

The peak frequency of sunlight is yellow-green, which is also the color that our eyes are most sensitive to.

Question 12

How do dolphins perceive their environment in dark and murky water?

Answer 12

Dolphins emit ultrasound and then time its echoes.

Question 13

What happens to the direction of the magnetic field about an electric current when the direction of the current is reversed?

Answer 13

The magnetic field reverses direction.

Question 13

How does the speed of light that emerges from a pane of glass compare with the speed of light incident on the glass?

Answer 13

The incident and emerging speeds of light are the same.

Question 14

What do we call two colors that add to produce white?

Answer 14

Two colors that add to produce white are called complementary colors.

Question 16

Is polarization a property of transverse waves, longitudinal waves, or both?

Answer 16

Polarization is ONLY a property of TRANSVERSE waves.

Question 17

Which is induced by the rapid alternation of an electric field?

Answer 17

An alternating magnetic field is induced.

Question 18

Compared to the distance of an object in front of a plane mirror, how far behind the mirror is the image?

Answer 18

Image distance and object distance are the same.

Question 19

In what direction are the vibrations in a transverse wave, relative to the direction of wave travel? In a longitudinal wave?

Answer 19

Vibrations in a transverse wave are perpendicular to wave travel.Parallel to wave travel in longitudinal waves.

Question 21

What is the relationship between refraction and the speed of light?

Answer 21

The speed of light slows when the light is refracted in a medium.

Question 23

Why does the Sun look reddish at sunrise and sunset?

Answer 23

High frequency blue light is scattered all along the path of sunlight, at sunrise or sunset the path has much blue missing.

What remains is light of lower frequencies, which accounts for the reddish color of the Sun at these times.

Question 24

Why is iron magnetic and wood not magnetic?

Answer 24

Iron has magnetic domains; wood does not.

Question 25

In what way are magnetic poles very different from electric charges?

Answer 25

Magnetic poles cannot be isolated.

Question 25

What happens to the direction of the magnetic force on a wire in a magnetic field when the current in the wire is reversed?

Answer 25

When the current is reversed, the magnetic force acts in the opposite direction.

Question 26

In the Doppler effect, does frequency change?Does wavelength change? Does wave speed change?

Answer 26

Only frequency and wavelength change in the Doppler effect, NOT wave speed.

Question 26

In what region of the electromagnetic spectrum is the resonant frequency of electrons in glass?

Answer 26

The resonant frequency of electrons in glass is in the ultraviolet region.

Question 27

What is the principal difference between a radio wave and light? What about between light and an X-ray?

Answer 27

The principal difference among radio, light, and X-rays is frequency.

Question 29

What is a mirage?

Answer 29

A mirage is a distorted view in which refracted light appears as if it is reflected light.

Question 30

Which of these does a transformer change: voltage, current, energy, power?

Answer 30

A transformer changes **voltage** and **current.**

Question 32

What physical phenomenon underlies beats?

Answer 32

Interference is the phenomenon underlying beats.

Question 33

What two kinds of motion are exhibited by electrons in an atom?

Answer 33

Electron Spin and Electron Revolution about the Nucleus.

Question 34

What is absorbed by water to give it a cyan color?

Answer 34

Infrared and red light are absorbed by water. Absorption of red produces the complementary color, cyan.

Question 35

Is it correct to say that an electric motor is a simple extension of the physics that underlies a galvanometer?

Answer 35

Yes; the difference is that the rotation in a motor continues, whereas in a galvanometer the deflection is momentary.

Question 37

What is the source of all waves?

Answer 37

The source of all waves is a vibrating object.

Question 38

Why do troops "break step" when crossing a bridge?

Answer 38

Troops "break step" in order to avoid marching in rhythm with the natural frequency of the bridge--to prevent resonance.

Question 39

How does the range of refrigerator magnets compare with the range of common bar magnets?

Answer 39

Refrigerator magnets are shorter range than common bar magnets.

Question 40

Relate wave speed and bending to the phenomenon of refraction.

Answer 40

Refraction occurs when parts of the wave fronts of sound travel at different speeds and produce bending in the direction of the waves.

Question 41

Will light pass through a pair of Polaroid filters when their air axes are aligned? What about.... When their axes are at right angles to each other?

Answer 41

Light will pass through filters when their axes are aligned, but NOT when their axes are at right angles to each other.

Question 42

What prevents rainbows from being seen as complete circles?

Answer 42

The ground gets in the way, cutting off the view of a whole circular rainbow.

Question 43

Is it correct to say that a generator produces energy?

Answer 43

No; a generator transforms energy from one form into another.

Question 44

State Faraday's Law.

Answer 44

The induced voltage in a coil is proportional to the number of loops multiplied by the rate at which the magnetic field changes within those loops.

Question 45

Is the current produced by a common generator ac or dc?

Answer 45

The current is AC because the induced voltage is AC.