Chapter 20

$$ \begin{aligned} &\text { What is the energy of a photon of electromagnetic radiation with frequency }\\\ &8.95 \times 10^{10} \mathrm{~Hz} ? \end{aligned} $$

$$ \begin{aligned} &c=3.00 \times 10^{8} \mathrm{~m} / \mathrm{s} \\ &\lambda=4.55 \times 10^{-5} \mathrm{~m} \\ &f=? \end{aligned} $$

$$ \begin{aligned} &\text { What is the frequency of a photon of electromagnetic radiation with energy }\\\ &3.96 \times 10^{-22} \mathrm{~J} ? \end{aligned} $$

$$ \begin{aligned} &c=3.00 \times 10^{8} \mathrm{~m} / \mathrm{s} \\ &\lambda=9.70 \times 10^{-10} \mathrm{~m} \\ &f=? \end{aligned} $$

Find the distance (in metres) traveled by a light wave in \(6.40 \mathrm{~s}\).

$$ \begin{aligned} &c=3.00 \times 10^{8} \mathrm{~m} / \mathrm{s} \\ &f=9.70 \times 10^{11} \mathrm{~Hz} \\ &\lambda=? \end{aligned} $$

$$ \text { Find the frequency of electromagnetic radiation with energy } 2.00 \times 10^{-24} \mathrm{~J} \text { . } $$

$$ \begin{aligned} &c=3.00 \times 10^{8} \mathrm{~m} / \mathrm{s} \\ &f=24.2 \mathrm{MHz} \\ &\lambda=? \end{aligned} $$

$$ \text { Find the frequency of electromagnetic radiation with energy } 5.50 \times 10^{-26} \mathrm{~J} \text { . } $$

$$ \begin{aligned} &c=3.00 \times 10^{8} \mathrm{~m} / \mathrm{s} \\ &f=45.6 \mathrm{MHz} \\ &\lambda=? \end{aligned} $$

$$ \begin{aligned} &\text { Find the energy of a photon of electromagnetic radiation with frequency }\\\ &2.50 \times 10^{12} \mathrm{~Hz} \end{aligned} $$

$$ \begin{aligned} &c=3.00 \times 10^{8} \mathrm{~m} / \mathrm{s} \\ &f=415 \mathrm{~Hz} \\ &\lambda=? \end{aligned} $$

$$ \text { Find the frequency of electromagnetic radiation with energy } 3.65 \times 10^{-23} \mathrm{~J} . $$

$$ \begin{aligned} &\text { Find the energy of a photon of electromagnetic radiation with frequency }\\\ &9.20 \times 10^{16} \mathrm{~Hz} \end{aligned} $$

$$ \begin{aligned} &c=3.00 \times 10^{8} \mathrm{~m} / \mathrm{s} \\ &\lambda=9.23 \mathrm{~km} \\ &f=? \end{aligned} $$

Find the wavelength of a radio wave from an AM station broadcasting at a frequency of \(14 \overline{0} 0 \mathrm{kHz}\).

Find the wavelength of a radio wave from an FM station broadcasting at a frequency of \(10 \overline{0}\) MHz.

How far away (in \(\mathrm{km}\) ) is an airplane if the radar wave returns to the scanning radar unit in \(1.24 \times 10^{-3}\) s?

Find the frequency of an electromagnetic wave if its wavelength is \(85.5 \mathrm{~m}\).

An auto mechanic uses a strobe light to time a classic car engine. If the light is held \(0.20 \mathrm{~m}\) from the flywheel and the mechanic's eye is \(0.75 \mathrm{~m}\) from the strobe, how long does it take the light from the strobe to reach the mechanic's eye?

Find the intensity of a light source that produces illumination of \(5.50 \mathrm{ft}-\) candles at \(9.85 \mathrm{ft}\) from the source.

An AM radio signal has a frequency of \(65 \overline{0} \mathrm{kHz}\). What is the energy of a photon of that electromagnetic radiation?

$$ \text { Find the frequency of an electromagnetic wave if its wavelength is } 3.25 \times 10^{-8} \mathrm{~m} \text { . } $$

(a) How long does it take for light to reach the earth from Mars when the separation of the two planets is at its smallest? The earth's orbital radius is 143 million kilometres. The orbital radius of Mars is 218 million kilometres. (b) How long does it take when the separation is at its maximum? Assume the planetary orbits are circular. Also make the (nonphysical) assumption that the sun is transparent to the transmission of light between the planets.

Find the intensity of a light source that produces an illumination of \(5.28\) lux at \(6.50 \mathrm{~m}\) from the source.

If it takes \(4.31\) years for light to reach the earth from Alpha Centauri, the closest star to the earth other than the sun, what is the distance (in miles) to the next nearest neighbor (Barnard's Star), which is \(25 \%\) farther away?

If an observer triples her distance from a light source: (a) Does the illumination at that point increase or decrease? (b) In what proportion does the illumination increase or decrease?

How long does it take light to reach the earth from Jupiter when the separation of the two planets is (a) at its smallest and (b) at its largest? The earth's orbital radius is 143 million kilometers. The orbital radius of Jupiter is 725 million kilometers. Assume the planetary orbits are circular. Also, make the (nonphysical) assumption that the sun is transparent to the transmission of light between the planets.

An AM radio station broadcasts a signal with a wavelength of \(237 \mathrm{~m}\). Find its frequency in \(\mathrm{kHz}\).

Preparing for reentry, astronauts use radar to determine the distance back to the earth. What is their altitude if it takes \(0.330 \mathrm{~s}\) for the radar wave to travel to the earth and return?

The distance to the moon can be calculated by reflecting a ray of light off a mirror left by astronauts. The light travels to the mirror and back in \(2.56 \mathrm{~s}\). Find the distance to the moon.

Light from the sun travels \(1.50 \times 10^{8} \mathrm{~km}\) to reach the earth. How long does its journey take in minutes?