PHY112-2 Final

Explain why light is generally considered unpolarized even though individual EM waves are polarized.

EM rays are random so there is no uniform polarization

Person A is on Earth and person B is on a spaceship moving at near light speeds. Which of the following statements regarding the measured times is most accurate?

Each person measures the other person's clock as slow.

Which of the following is a true statement?

Electric fields direct away from positive charges and towards negative charges.

Which of the following is a true statement?

Electromagnetic waves deliver an oscillating amount of energy to a given area of space each second.

What is Huygens' principle?

Every point on a wave front produces spherical wavelets that expand outwards. A line drawn tangent to all of the wavelets produced by a particular front will show the location of the new wave front.

All observers in all inertial frames of reference will measure the same noncausal events taking place in the same order: event A, then event B, and then event C.

False

How will each of the following changes affect the spacing between the fringes and the central maxima? - Increased distance between double slits - Increased wavelength sent through double slits - Increased distance between barrier and the screen

If d increases, the fringes move closer to the central maxima. If λ increases, the fringes move further away from the central maxima. If L increase, the fringes move closer to the central maxima.

A wire loop sits motionless in a uniform magnetic field as shown below. Which of the following changes will induce a clockwise current in the loop?

Increase the magnetic field strength.

Which of the following is a true statement?

Induced emf is proportional to the rate of change of flux.

Which of the following experimental results helps prove the wave nature of light (i.e., which results can only be explained through wave behavior)?

Interference pattern that forms when light passes through two small slits in a barrier.

1. Explain how polarizing sunglasses help to reduce glare from the road.

Polarizing sunglasses are vertically oriented filters and so will block these horizontal reflections. This reduces road glare while driving, and makes it easier to see the road.

What is the difference between visible light and radio waves? Why can't your eyes see radio waves?

Radio waves are longer and lower frequency than visible light waves. The wavelength is too large for human eyes to detect

What is the difference between a radio wave and a sound wave?

Radio waves are transverse EM waves created through the oscillation of charge. Sound waves are longitudinal waves created by oscillating the pressure on some material

Which of the following circuit components will function the same regardless of whether the voltage source is direct or alternating?

Resistors

Which of the following terms is NOT relativistic (i.e., does not depend on the relative velocities between frames of reference)?

Rest mass

A light emitter broadcasts a beam of light to the right. Three observers measure the speed of the light ray after it was emitted. Observer A is standing still relative to the light emitter. Observer B is moving to the right relative to the light emitter. Observer C is moving to the left relative to the light emitter. Which will measure the greatest light speed?

The observers measure the same light speed.

A student drops a permanent magnet through a copper pipe. The magnet takes a very long time to drop out the bottom of the pipe. Explain this behavior. (Copper is not ferromagnetic.)

The pipe acts as a loop of wire. As the magnet falls through the loop of wire, it induces an EMF, which results in a current in the copper wire. The magnetic field created by this current opposes the pull of gravity, and the falling acceleration is reduced

A wire loop moves into a magnetic field as shown below. Which of the following will result?

This will induce a counterclockwise current in the loop.

What is the purpose of a transformer?

Transformers change the voltage in a circuit.

All observers in all inertial frames of reference will measure the same causally linked events taking place in the same order: event A, then event B, and then event C

True

Relative to a clock on Earth, when the clock on Earth has measured the passage of one hour, a fast-moving clock will have measured the passage of less than one hour.

True

Which of the following best describes two similar triangles?

Two triangles that have two angles that measure the same.

What is the difference between visible light and ultraviolet (UV) rays? Why can't your eyes see UV rays?

Ultraviolet waves are shorter and higher frequency than visible light waves. The wavelength is too short for human eyes to detect

The electromotive force is most closely related to:

Voltage

The primary difference between x-ray waves and radio waves is

X-ray waves are higher frequency.

The length of a linear broadcasting antenna is oriented in the y plane. A linear receiving antenna should be oriented in the

Y plane.

You place an arrow in front of a converging mirror at some position do > 2f. You observe the position of the image and place a piece of paper at the image position. What will you observe on the paper?

You will see a small, upright arrow.

A maximum peak in an oscillating magnetic field occurs at some time t. At the same time t, the electric field will experience

a maximum peak.

Which of the following has the fastest speed? a) Radio waves b) Blue light c) X-rays

all have same speed

The angle of refraction that occurs at a boundary is dependent on:

all of the above

The wavelength is the distance measured:

all of the above

Which of the following is an accurate conclusion of the momentum-energy relationship?

all of the above

Reflection is best described as:

an equal angle bounce off a barrier.

What is an inertial frame of reference? What is a noninertial frame of reference?

an object with no net force will move with a constant velocity, and an object with a net force will accelerate.

Alternating current is the best described as:

current that changes direction and changes magnitude.

A student shines white light through a diffraction grating with 8000 lines per cm, how do you find d?

d = (1 cm) / (8000 lines) (1 m / 100 cm) = 1.25E-6 m

Current is caused by:

electric potential differences.

A light ray is incident on a plane mirror with an angle of 50°. The reflected angle of the light ray is

equal to 50°.

An observer measures the length (L), width (w), and height (h) of a box while stationary relative to the box. The observer then travels at near light speeds parallel to the length (L) of the box. If the observer measures the width (w) of the box while moving, the measured value will now be

equal to w

A muon is a type of particle with a life span of time t. If the particle moves very fast relative to a stationary scientist, the scientist will measure the life span at a time less than t.

false

A particle has a particular life span of time t. If the particle moves very fast, relative to a stationary observer, the observer will observe that the life span of the particle is

greater than t.

An object with a height of 1.0 cm is at some position from a converging mirror. The image is real and has a height of 0.33 cm. The statement that best compares the object and image positions is the

image is closer the mirror than the object.

When solving for the image distance, a resulting negative value for di indicates the

image is virtual.

A student shines a monochromatic light through a diffraction grating and observes the resulting interference pattern on a screen. If the student wishes to move the first order fringes closer to the central maxima, the student should

increase the distance between the slits in the diffraction grating.

Relative to a stationary object, a fast-moving object will experience time:

less time.

Which of the following terms is no longer conserved in different inertial frames of reference?

momentum

A wire oriented along the vertical edge of the screen has current moving in the upward direction. If the wire is in a field directed from right to left across the screen, the wire will experience a force directed:

out of the screen.

Wave intensity is defined as the

rate of energy delivered to a certain area.

If the object distance from the mirror is greater than the focal length, the image will be

real and inverted

A light ray traveling through a material with an index of refraction of 1.2 is incident on a material that has an index of refraction of 1.4. Compared to the incident angle, the refracted angle of the light ray is

smaller than the incident angle.

Which of the following diagrams correctly shows the path that light will take through the triangular prism?

straight, angle down, angle down

One twin gets into a rocket, and travels at 75% the speed of light away from the Earth. Relative to the twin on the Earth, when the Earth twin has aged 5 years, how much time will the rocket twin have experienced? t = to / (sqrt(1 - v^2 / c^2))

t = 3.3 years

The angle of reflection that occurs at a boundary is dependent on:

the angle of incidence.

Refraction is best described as:

the change in direction experienced by light passing through a boundary.

Voltage is best described as:

the difference in the energy per charge ratio between two points in an electric field.

The wave amplitude refers to:

the height of a transverse wave measured from equilibrium to crest or trough and the maximum displacement of a particle in a wave from its equilibrium position.

An object is placed in front of a double convex (converging) lens, and the image is located. A screen is placed at the image location. The screen is then moved backwards. How will the image appear on the screen now?

the image will get blurrier

An object is placed in front of a double convex (converging) lens, and the image is located. A card is placed between the image and the lens. The effect the card will have on the image is:

the image will get darker

Wave frequency refers to:

the number of wave oscillations that occur in a second.

Which is faster, an EM wave with a high frequency or an EM wave with a low frequency? Explain.

the same

The reason why humans cannot see infrared waves is because

the waves are too long for human eyes to detect.

The Lorentz factor is the factor multiplier that indicates the difference in relativistic times between two different inertial frames of reference.

true

It is not possible for an object with mass to travel at the speed of light.

true Only massless objects can travel at the speed of light

An object is at a position 6.0 cm from a converging lens with a focal length of 3.0 cm. The position of the image relative to the lens is 1/f = 1/di + 1/do

+6.0 cm.

A wave front can correctly be described as

All of the above

Wave intensity is most closely related to:

All of the above

The focal length of a lens depends on the

All of the above statements are correct.

Which of the following factors will affect the intensity of an EM wave?

Amplitude

Which of the following is NOT a true statement?

An object with some mass floating motionless in space has no energy.

A ray diagram showing the principle rays traveling from the tip of an arrow through a converging lens is below. An additional ray is also incident on the lens. Which of the rays shows the correct refraction for this ray?

B

Which of the following is a true statement?

Both of the above statements are true.

A ray diagram showing the principle rays traveling from the tip of an arrow through a converging mirror is below. An additional ray is also incident on the mirror. Which of the rays shows the correct reflection for this ray?

C

An object with a height of 2.0 cm is at a position 6.0 cm in front of a converging lens. An observer notes that the image is upright and has a height of 4.0 cm. What is the focal length of the lens? hi/ho=−di/do 1/f=1/do+1/di

12 cm

What is the electric field strength of an EM wave if the peak intensity of the wave is 5000 W/m2? Eo=(Iavg/cEo) ^1/2 c = 3x10^8 eo= 8.85x110^-12

1372 W/m2

A particular electromagnetic wave has a peak magnetic field strength of 5 x 10-5 T. What is the average intensity of the electromagnetic wave? Emax=Bc Iavg = (Emax)^2ec/(2)

2.99 x 105 W/m2

Red light has a wavelength of 6.5 x 10-7 m. What is the frequency of red light? c = λf

4.6 x 1014 Hz

At what speed must an object move so that its total energy is 10% greater than its rest energy?

42% of the speed of light

An astronaut traveling at a speed 75% the speed of light has traveled a distance of 3.5 x 107 km. From the perspective of a stationary observer, how far will the astronaut travel? L = Lo / γ y=sqrt(1 - (0.75c)2 / c2)]

5.3 x 107 km

A red light wave (λ = 650 nm) refracts from air into water (n = 1.3). As a result, the wavelength of the red light in the water is λ' = λ / n

500 nm.

What is the critical angle of a light ray traveling through a material 1 (n = 1.6) incident on material 2 (n = 1.3)? n1sinθ1=n2sinθ2

54.3°

What is the largest fringe order that will result from shining a red laser (λ = 650 nm) through a barrier with two slits spaced 5 x 10-6 m apart? dy/L = mλ

7

You place an object in front of a mirror and observe that the image is real. Which of the following arrangements could produce this image?

A converging lens, but only if the object is placed at do > f.

Which of the following accurately describes a transverse wave?

A wave whose particles oscillate perpendicular to the direction of wave motion

Observer A sees a dog chase a cat (event 1), which causes the cat to climb a tree (event 2). Observer B moves at a constant, near light speed relative to observer A. Which statement is most accurate?

Observer B will always observe event 1 before event 2.

Light travels at a speed of 2.63x108 m/s through a particular material. What is the critical angle for that material? n = c/v n1sinθ1 = n2sinθ2

1.14, 61.3 degrees

What is the kinetic energy of a 2.0 kg object that is moving at 83% of the speed of light? K=(γ−1)mc2 K = (1 / sqrt (1 - (0.83c)2/c2) - 1)(2 kg)(3x108 m/s)

1.4 x 1017 J

An object is at a position of 15 cm from a diverging lens with a virtual focal point of 8 cm. The location of the image is 1/f = 1/di + 1/do

-5.2 cm.

A particular inductor is connected to a circuit where it experiences a change in current of 0.8 amps every 0.10 sec. If the inductor has a self-inductance of 2.0 V, what is the inductance? V=−L(I/t)

0.25 H

An arrow flies past a person standing on Earth. When at rest with respect to the Earth, the arrow's length measures 1.00 m. What is the arrow's length as measured by the person on Earth when the arrow moves at 2.7 x 108 m/s? L = Lo / γ y = sqrt(1 - (2.7x10^8m/s) / c2)]

0.44m

What is the rest energy of an object that has a mass of 2.0 kg?

1.8 x 1017 J

An observer measures the length (L), width (w), and height (h) of a box while stationary relative to the box. The observer then travels at near light speeds parallel to the length (L) of the box. If the observer measures the length (L) of the box while moving, the measured value is

Less than L

Which of the following is a true statement?

Magnetic fields cannot have monopoles.

When mass travels at near light speeds, the classic definition of momentum (p = mv) cannot be used to approximate true momentum. Which of the following best explains this?

Momentum and velocity do not have a linear relationship.

An object is at a position 3.0 cm from a converging lens with a focal length of 3.0 cm. The image is best described as

No image will form.

Which of the following statements regarding radio waves and sound waves is accurate?

None of the above statements are accurate.

If the object distance from the mirror is less than the focal length, the image will be

virtual and upright

An object is at a position 2.0 cm from a converging lens with a focal length of 3.0 cm. The image is best described as

virtual and upright.

An object is at a position of 6.0 cm from a diverging lens with a focal length of 3.0 cm. The image can best be described as

virtual and upright.

Images produced with diverging lenses are always

virtual and upright.

If a magnetic field oscillates in the +/- x plane and the electric field oscillates in the +/- z plane, then the direction of the traveling light wave will be:

y plane