A Wave Travelling along Z

solved ElectromagneticWave

Q. A plane electromagnetic wave travels in vacuum along z-direction. If the frequency of the wave is 30 MHz $ν = 30$ MHz, what is its wavelength, in metres?

Inputs

frequency

ν

30 MHz

Outputs

wavelength

λ

How it's solved

Solved with ElectromagneticWave

Given

$ν = 30$ MHz

Find $λ$ .

Working

$ν = 30$ MHz $= 3 \times 10^{7}$ Hz
light travels at c(wave) $c = ν \cdot λ$
$2.99792458 \times 10^{8} = 3 \times 10^{7} \cdot λ$
$λ = 9.99 m$
$λ \approx 10$ mto 2 significant figures

Conclusion

Every electromagnetic wave in vacuum travels at the speed of light, so its wavelength is that speed over its frequency.

The web of concepts

given read from the words equation asked

The Ruby that solves it

The question and its solution are small Ruby files. The engine runs them.

question.rb

1require_relative "../physics"23question :a_wave_travelling_along_z do4  kind :numerical5  describes "A plane electromagnetic wave travels in vacuum along z-direction. If the frequency of the wave is " \6            "%{frequency}, %{wavelength}, in metres?"7  given frequency: "30 MHz"8  asks wavelength: "what is its wavelength"9end

solution.rb

1require_relative "../questions/a_wave_travelling_along_z"2require_relative "../science/electromagnetic_waves/electromagnetic_wave"34solve :a_wave_travelling_along_z, using: ElectromagneticWave do5  objects :wave67  take frequency: wave.frequency89  wavelength = wave.wavelength10  answer wavelength:, in: "m", figures: 21112  conclusion "Every electromagnetic wave in vacuum travels at the speed of light, so its wavelength is that " \13             "speed over its frequency."14end

playground.rb

1require_relative "../solutions/a_wave_travelling_along_z"23play_with :a_wave_travelling_along_z do4  title "A Wave Travelling along Z"5end

The laws it drew on

quantity	written	units	within	from
pi	$π$	—	0 … ∞	ElectromagneticWave
speed of light	$c$	m/s	—	ElectromagneticWave
electric field	$E$	V/m	—	ElectromagneticWave
magnetic field	$B$	T	—	ElectromagneticWave
wave number	$k$	m⁻¹	—	ElectromagneticWave
angular frequency	$ω$	rad/s	—	ElectromagneticWave
wavelength	$λ$	m	0 … ∞	ElectromagneticWave
frequency	$ν$	Hz	0 … ∞	ElectromagneticWave
electric field of ground	$E_{g}$	V/m	—
magnetic field of ground	$B_{g}$	T	—
electric field of wave	$E$	V/m	—
magnetic field of wave	$B$	T	—
wave number of ground	$k_{g}$	m⁻¹	—
wavelength of ground	$λ_{g}$	m	0 … ∞
wave number of wave	$k$	m⁻¹	—
wavelength of wave	$λ$	m	0 … ∞
angular frequency of ground	$ω_{g}$	rad/s	—
frequency of ground	$ν_{g}$	Hz	0 … ∞
angular frequency of wave	$ω$	rad/s	—
frequency of wave	$ν$	Hz	0 … ∞

E_{w} = c \cdot B_{w}

fields of a light wave

k_{w} = \frac{2 \cdot π}{λ_{w}}

wave number and wavelength

ω_{w} = 2 \cdot π \cdot ν_{w}

angular frequency and frequency

c = ν_{w} \cdot λ_{w}

light travels at c

E_{g} = c \cdot B_{g}

fields of a light wave(ground)

E = c \cdot B

fields of a light wave(wave)

k_{g} = \frac{2 \cdot π}{λ_{g}}

wave number and wavelength(ground)

k = \frac{2 \cdot π}{λ}

wave number and wavelength(wave)

ω_{g} = 2 \cdot π \cdot ν_{g}

angular frequency and frequency(ground)

ω = 2 \cdot π \cdot ν

angular frequency and frequency(wave)

c = ν_{g} \cdot λ_{g}

light travels at c(ground)

c = ν \cdot λ

light travels at c(wave)