Question 1

In an RC circuit, which of the following is a possible phase angle?
A)45$\degree$
B)-45$\degree$
C)135$\degree$
D)-135$\degree$

Accepted Answer

The answer of In an RC circuit, which of the...

Question 2

Temperature variation of different parts of a person's body can be detected by analyzing the emission pattern of which type of electromagnetic radiation?
A)microwave
B)infrared
C)ultraviolet
D)x-rays

Accepted Answer

Infrared radiation is emitted by objects at different temperatures, including the human body. By analyzing the emission pattern of infrared radiation, it is possible to determine the temperature variation in different parts of a person's body. Microwave, ultraviolet, and x-rays are not typically used to detect temperature variation in the human body.

Question 3

Of the various types of electromagnetic radiation, which is the most penetrating through all forms of matter?
A)infrared
B)gamma
C)visible light
D)ultraviolet

Accepted Answer

Gamma radiation has the highest energy and shortest wavelength among all types of electromagnetic radiation. This property allows it to penetrate through all forms of matter, including concrete and steel, making it the most penetrating form of electromagnetic radiation. In contrast, infrared, visible light, and ultraviolet radiation have lower energy levels and longer wavelengths, which limits their ability to penetrate through dense materials.

Question 4

In a 60-Hz RLC circuit, the phase angle is positive.The values of the resistance, inductance, and the capacitance are now doubled.Which of the following is now true about the phase angle?
A)It is still positive.
B)It could be zero.
C)It will be negative.
D)It could be positive, negative, or zero, but it cannot be greater than its original value.

Accepted Answer

Doubling the resistance, inductance, and capacitance in an RLC circuit does not change the sign of the phase angle. The phase angle's sign is determined by the dominant component (inductive or capacitive). If the phase angle was positive (indicating an inductive circuit where the voltage leads the current), doubling all components keeps the circuit inductively dominant, thus maintaining a positive phase angle.

Question 5

In an RLC circuit, the maximum current is 1 amp.What is the average current?
A)  A
B)  A
C)(1/2) A
D)None of the above.

Accepted Answer

The answer of In an RLC circuit, the maximum current...

Question 6

An ultraviolet light wave has a wavelength of 300 nm and speed of 2.1 * 10⁸m/s through a transparent medium.What is the frequency of this wave in the medium? (1 nm = 10^-9 m and c = 3.00 * 10⁸ m/s) A)6.3 * 10²Hz B)9.0 * 10² Hz C)7.0 * 10¹⁴ Hz D)10 * 10¹⁴Hz

Accepted Answer

The answer of An ultraviolet light wave has a wavelength...

Question 7

An observer is moving in space toward a distant star at 100 km/s while the star is moving toward the observer at 200 km/s; the relative velocity being 300 km/s of approach.What relative change in frequency of the light from the star as seen by the observer? (The speed of light in space is 3.00 * 10⁵ km/s). A)0.10% increase B)0.10% decrease C)0.067% increase D)0.033% decrease

Accepted Answer

The relative change in frequency can be calculated using the formula: 
Δf/f = (v/c) / (1 - (v/c))
where Δf is the change in frequency, f is the original frequency, v is the relative velocity, and c is the speed of light.
Plugging in the given values, we get:
Δf/f = (300/300000) / (1 - (300/300000))
Δf/f = 0.001 / 0.999
Δf/f = 0.001001

This means there is a 0.1001% increase in frequency. However, the question only asks for the relative change in percentage, so we need to express this value as a percentage:
Δf/f = 0.1001%

Rounding to two significant figures, the answer is 0.067% increase, which is choice C.

Question 8

An object that is giving off only infrared electromagnetic waves is giving off heat through:
A)convection.
B)conduction.
C)radiation.
D)visible light.

Accepted Answer

Infrared electromagnetic waves are a type of radiation, and heat transfer through radiation is the process by which energy is emitted by a heated object in the form of electromagnetic waves, including infrared radiation. Therefore, the best choice is C - radiation.

Question 9

Microwave radiation is useful in which of the following?
A)sending phone messages
B)cooking food
C)aircraft navigation
D)All of the above are valid choices.

Accepted Answer

Microwave radiation is useful in all of the given choices. It is used in sending phone messages via cell phone networks, cooking food through microwave ovens, and in aircraft navigation through radar systems.

Question 10

In the Doppler effect for electromagnetic waves, which of the following gives the greatest shift in frequency?
A)the source moving toward the non-moving observer at speed v
B)the observer moving toward the non-moving source at speed v
C)the source moving toward the approaching observer, both at speed v/2
D)All of the above give the same shift.

Accepted Answer

The Doppler effect for electromagnetic waves, such as light, does not depend on the relative motion of the source and observer in the same way it does for sound. The observed frequency shift is determined by the relative velocity between the source and the observer. Therefore, whether the source is moving towards a stationary observer, the observer is moving towards a stationary source, or both are moving towards each other with equal but halved speeds, the relative velocity—and thus the frequency shift—is the same in all scenarios.

Question 11

The electromagnetic radiation that causes tanning:
A)can produce cancer.
B)rarely passes through glass windows.
C)is absorbed by ozone.
D)is all of the above.

Accepted Answer

Electromagnetic radiation that causes tanning can produce cancer, rarely passes through glass windows, and is absorbed by ozone. Therefore, all of the above options are correct.

Question 12

The Doppler shift for electromagnetic radiation from distant galaxies moving away from the observer is called a:
A)red shift.
B)blue shift.
C)black shift.
D)vacuum shift.

Accepted Answer

When a distant object is moving away from an observer, the wavelength of its electromagnetic radiation appears longer, and thus, the light shifts towards the red end of the spectrum. This is called the red shift, and it is one of the primary pieces of evidence for the expanding universe.

Question 13

Find the frequency of x-rays of wavelength 10^-10m.(c = 3 * 10⁸ m/s) A)3 * 10¹⁸ Hz B)3 * 10¹⁶Hz C)6 * 10⁹ Hz D)3 * 10⁸ Hz

Accepted Answer

The answer of Find the frequency of x-rays of wavelength...

Question 14

An RLC circuit has resistance R₀, inductance L₀, and capacitance C₀.If the resistance value is now doubled, which values of inductance and capacitance will result in the same resonant frequency as before. A)2L₀, 2C₀ B)L₀/2, C₀/2 C)2L₀, C₀/2 D)2L₀, C₀

Accepted Answer

The resonant frequency of an RLC circuit is given by the formula f = 1/(2π√(LC)). If we double the resistance, the resonant frequency will remain the same only if we halve the capacitance or double the inductance. Therefore, the correct choice is 2L₀, C₀/2. Choice A is incorrect because it doubles both inductance and capacitance. Choice B is incorrect because it halves both inductance and capacitance. Choice D is incorrect because it doubles both inductance and capacitance without halving anything.

Question 15

What is the wavelength of 100-MHz television EM waves? (c = 3 * 10⁸ m/s) A)0.3 cm B)3 m C)9 km D)10 m

Accepted Answer

The answer of What is the wavelength of 100-MHz television...

Question 16

The human eye is sensitive to light with wavelength down to 390 nm.What is the frequency of radiation at this wavelength? (1 nm = 10^-9 m and c = 3.00 * 10⁸ m/s) A)1.8 * 10⁸ Hz B)8.5 * 10⁸ Hz C)1.1 * 10¹¹ Hz D)7.7 * 10¹⁴ Hz

Accepted Answer

The answer of The human eye is sensitive to light...

Question 17

A monochromatic light wave in vacuum has frequency f₀ and wavelength l₀.Which of the following are also possible frequency and wavelength combinations for a monochromatic light wave in vacuum? A)2f₀, 2l₀ B)f₀/2, l₀/2 C)2f₀, l₀/2 D)None of the above are possible.

Accepted Answer

Option A is not possible as frequency and wavelength are inversely proportional in vacuum according to the formula c = fλ, where c is the speed of light.
Option B is not possible as frequency and wavelength change in the same proportion. Therefore, if one is halved, the other is halved too.
Option C is possible as doubling the frequency and halving the wavelength will keep the speed of light constant.
Option D is incorrect as option C is a valid possibility.

Question 18

As an electromagnetic wave travels through free space, its speed can be increased by:
A)increasing its frequency.
B)increasing its energy only.
C)increasing both its energy and momentum.
D)None of the above will increase its speed.

Accepted Answer

The speed of an electromagnetic wave through free space is determined solely by the properties of free space, namely, the permittivity and permeability of free space. Therefore, neither changing the frequency nor increasing the energy or momentum will increase the speed of the wave.

Question 19

What value of inductance should be used in a series circuit with a capacitor of 1.8 * 10^-3 mF when designed to radiate a wavelength of 35 m? (c = 3.00 * 10⁸ m/s) A)3.8 mH B)2.6 * 10^-2 mH C)3.8 * 10^-3 mH D)1.9 * 10^-4 mH

Accepted Answer

The formula to calculate the inductance in a series circuit with a capacitor to radiate a specific wavelength is:

L = (c^2 * C) / (4 * pi^2 * lambda^2)

Where:

L = inductance in henries
C = capacitance in farads
lambda = wavelength in meters
c = speed of light in meters per second
pi = 3.14159...

Substituting the given values:

L = (3.00 * 10^8 m/s)^2 * (1.8 * 10^-3 mF) / (4 * (3.14159)^2 * (35 m)^2)
L = 3.836 * 10^-3 H = 3.8 * 10^-3 H = 3.8 mH (rounded to one significant figure)

Therefore, the best choice is C (3.8 * 10^-3 H) as the value of inductance to be used in the circuit.

Quiz 21: Alternating Current Circuits and Electromagnetic Waves

In an RC circuit, which of the following is a possible phase angle?

Temperature variation of different parts of a person's body can be detected by analyzing the emission pattern of which type of electromagnetic radiation?

Of the various types of electromagnetic radiation, which is the most penetrating through all forms of matter?

In a 60-Hz RLC circuit, the phase angle is positive.The values of the resistance, inductance, and the capacitance are now doubled.Which of the following is now true about the phase angle?

In an RLC circuit, the maximum current is 1 amp.What is the average current?

An ultraviolet light wave has a wavelength of 300 nm and speed of 2.1 * 108 m/s through a transparent medium.What is the frequency of this wave in the medium? (1 nm = 10-9 m and c = 3.00 * 108 m/s)

An object that is giving off only infrared electromagnetic waves is giving off heat through:

Microwave radiation is useful in which of the following?

In the Doppler effect for electromagnetic waves, which of the following gives the greatest shift in frequency?

The electromagnetic radiation that causes tanning:

The Doppler shift for electromagnetic radiation from distant galaxies moving away from the observer is called a:

Find the frequency of x-rays of wavelength 10-10 m.(c = 3 * 108 m/s)

An RLC circuit has resistance R0, inductance L0, and capacitance C0.If the resistance value is now doubled, which values of inductance and capacitance will result in the same resonant frequency as before.

What is the wavelength of 100-MHz television EM waves? (c = 3 * 108 m/s)

The human eye is sensitive to light with wavelength down to 390 nm.What is the frequency of radiation at this wavelength? (1 nm = 10-9 m and c = 3.00 * 108 m/s)

A monochromatic light wave in vacuum has frequency f0 and wavelength l0.Which of the following are also possible frequency and wavelength combinations for a monochromatic light wave in vacuum?

As an electromagnetic wave travels through free space, its speed can be increased by:

What value of inductance should be used in a series circuit with a capacitor of 1.8 * 10-3 mF when designed to radiate a wavelength of 35 m? (c = 3.00 * 108 m/s)

An ultraviolet light wave has a wavelength of 300 nm and speed of 2.1 * 10⁸m/s through a transparent medium.What is the frequency of this wave in the medium? (1 nm = 10^-9 m and c = 3.00 * 10⁸ m/s)

Find the frequency of x-rays of wavelength 10^-10m.(c = 3 * 10⁸ m/s)

An RLC circuit has resistance R₀, inductance L₀, and capacitance C₀.If the resistance value is now doubled, which values of inductance and capacitance will result in the same resonant frequency as before.

What is the wavelength of 100-MHz television EM waves? (c = 3 * 10⁸ m/s)

The human eye is sensitive to light with wavelength down to 390 nm.What is the frequency of radiation at this wavelength? (1 nm = 10^-9 m and c = 3.00 * 10⁸ m/s)

A monochromatic light wave in vacuum has frequency f₀ and wavelength l₀.Which of the following are also possible frequency and wavelength combinations for a monochromatic light wave in vacuum?

What value of inductance should be used in a series circuit with a capacitor of 1.8 * 10^-3 mF when designed to radiate a wavelength of 35 m? (c = 3.00 * 10⁸ m/s)