Q: The speed of light in a vacuum is given by $$c = \frac{1}{\sqrt{\mu_0$ \$$epsilon_0$$}}. $$What are the values of $$\mu_0$ and $$\$$epsilon_0$$?

$$\mu_0$ = 4\pi \times 10$$^{-7}$$\ \mathrm{T\cdot m/A}$$ and $$\$$epsilon_0$$ = 8.85 \times 10$$^{-12}$$\ \mathrm{C^2$/(N\cdot m^2$)}$$

Q: If the frequency of visible light is $$7.9 \times 10$$^{14}$$\ \mathrm{Hz}$$, what is its wavelength?

$$3.8 \times 10$$^{-7}$$\ \mathrm{m}$$

Question 1

According to Faraday’s Law, what will happen to the induced emf in a coil if the magnetic field through the coil is increased at a faster rate?

Accepted Answer

The induced emf will increase because the rate of change of magnetic flux is greater.

Question 2

A coil with 20 turns and area $$0.0015\ \mathrm{m}^2 is $$placed perpendicular to a magnetic field that increases from $$0.050\ \mathrm{T} to$$ $$0.060\ \mathrm{T} in$$ $$0.10\ \mathrm{s}. $$What is the average induced emf?

Accepted Answer

$$0.03\ \mathrm{V}$$

Question 3

Which of the following best describes Lenz’s Law?

Accepted Answer

The induced current creates a magnetic field that opposes the change in the original flux.

Question 4

A copper ring is dropped vertically through a region with a constant horizontal magnetic field (into the page). At which positions does the ring experience an induced current?

Accepted Answer

Only when entering and exiting the field region.

Question 5

Which of the following is true about electromagnetic waves?

Accepted Answer

They are transverse waves and can travel through a vacuum.

Question 6

The speed of light in a vacuum is given by $$c = \frac{1}{\sqrt{\mu_0$ \$$epsilon_0$$}}. $$What are the values of $$\mu_0$ and $$\$$epsilon_0$$?

Accepted Answer

$$\mu_0$ = 4\pi 	imes 10$$^{-7}$$\ \mathrm{T\cdot m/A}$$ and $$\$$epsilon_0$$ = 8.85 	imes 10$$^{-12}$$\ \mathrm{C^2$/(N\cdot m^2$)}$$

Question 7

A radio station broadcasts at a frequency of $$91.9 	imes 10^6$\ \mathrm{Hz}. $$What is the wavelength of the radio wave?

Accepted Answer

$$3.26\ \mathrm{m}$$

Question 8

Why do astronomers say that observing a supernova 168,000 light-years away is like looking back in time?

Accepted Answer

Because the light from the supernova takes 168,000 years to reach Earth.

Question 9

Which property is NOT true for the image formed by a plane mirror?

Accepted Answer

The image is real.

Question 10

A person stands in front of a mirror. What is the minimum height of the mirror required for the person to see their full image?

Accepted Answer

Half the person's height.

Question 11

A person sits in front of two mirrors that intersect at a right angle. How many images of the person are seen?

Accepted Answer

Three

Question 12

Which equation correctly relates the speed of light $$c$$, wavelength $$\lambda$$, and frequency $$f of an $$electromagnetic wave?

Accepted Answer

$$c = \lambda f$$

Question 13

If the frequency of visible light is $$7.9 	imes 10$$^{14}$$\ \mathrm{Hz}$$, what is its wavelength?

Accepted Answer

$$3.8 	imes 10$$^{-7}$$\ \mathrm{m}$$

Question 14

Which of the following best describes the law of reflection for a flat mirror?

Accepted Answer

The angle of incidence equals the angle of reflection.

Question 15

Which of the following is a correct application of the right-hand rule (RHR) in electromagnetic induction?

Accepted Answer

Point your thumb in the direction of the induced current; your fingers curl in the direction of the magnetic field.

Question 16

A loop antenna is used to detect a radio wave. Which field component of the wave induces a current in the loop?

Accepted Answer

The magnetic field component perpendicular to the loop.

Question 17

Which region of the electromagnetic spectrum has the shortest wavelength?

Accepted Answer

Gamma rays

Question 18

A permanent magnet is moved toward a loop of wire connected to a resistor. According to Lenz’s Law, what is the direction of the induced current?

Accepted Answer

Such that the induced magnetic field opposes the increase in flux.

lecture 14

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