Electromagnetic Spectrum and Radiation

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AP Physics 2 › Electromagnetic Spectrum and Radiation

Questions 1 - 3

1

A beam of light is traveling at approximately $10\frac{m}{s}$ in a very dense medium. Given that the frequency of the light beam is , what is the wavelength of the light beam? Suppose that the speed of light in a vacuum is .

Explanation

The wavelength of the light beam doesn't depend on the speed through the medium. As such, as can solve for wavelength $\lambda$ by simply solving:

$\lambda f=c$

Where is frequency and is the speed of light in a vacuum.

$\lambda=\frac{c}{f}=\frac{3*10^8 \frac{m}{s}}{100\frac{1}{s}}=3*10^6m$

2

Determine the photon energy of orange light, $\lambda=605nm$ .

$3.29*10^{-19}J$

None of these

$8.44*10^{-19}J$

$6.11*10^{-19}J$

$2.45*10^{-19}J$

Explanation

Using

$E=\frac{hc}{\lambda}$

is the photon energy

is Plank's constant, $6.626*10^{-34}J*s$

is the speed of light, $3.00*10^8\frac{m}{s}$

$\lambda$ is the wavelength

Converting to and plugging in values:

$E=\frac{6.626*10^{-34}*3.00*10^{8}}{605*10^{-9}}$

$E=3.29*10^{-19}J$

3

Determine the frequency of orange light, $\lambda=605nm$ .

$4.96*10^{14}Hz$

None of these

$5.55*10^{14}Hz$

$8.19*10^{14}Hz$

$6.05*10^{14}Hz$

Explanation

Using

$c=\lambda* u$

Converting to and plugging in values

$3.00*10^8=605*10^{-9}* u$

$u=4.96*10^{14}Hz$

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