Question

How do you calculate the frequency of light if the given wavelength of light is 400nm ?
The speed of light is $3 \times 10^{8}$ m/s.

Answer 1

Hint : The frequency is defined as the number of waves that pass through a given point in space in a given time interval, which is usually one second. Cycles (waves) per second, or hertz, are the units of measurement. Color refers to the frequency of visible light, which ranges from 430 trillion hertz (red) to 750 trillion hertz (violet).

Complete Step By Step Answer:
The wavelength of light is divided by the speed of light to calculate frequency. When light travels through mediums other than the vacuum, its speed and wavelength change, so you must account for these changes when calculating the frequency.
Using the most common question, where c is the vacuum speed of light and is the wavelength the wavelength and velocity are given to you.
The other one is $E=h.f$ , which connects energy and frequency and gives you a value for h, Planck's constant, and photon energy, E.
When light travels through a vacuum, however, speed is actually a universal constant (or, to a very good approximation, air). In a vacuum, the measured speed of light (c) $2.9979\text{ }\times \text{ }{{10}^{8}}~m/s,$ or about $3.00\text{ }\times \text{ }{{10}^{8}}~m/s$ As a result, we have ,
$c\text{ }=\text{ }\lambda \nu$ .
The wavelength and frequency of light are related because the speed of light is constant: as one increases, the other decreases, and vice versa. This equation can be used to determine what one property of light must be given the other.
$\begin{aligned} & The\text{ }wavelength~\lambda ~and\text{ }frequency~\nu ~are\text{ }related\text{ }through\text{ }the\text{ } speed \text{ }of\text{ }light\text{ }in\text{ }vacuum~c~as: \\\ & c=\lambda \cdot \nu \\\ & So\text{ }using\text{ }your\text{ }data\text{ }we\text{ }get: \\\ & \nu =\dfrac{c}{\lambda }=\dfrac{3\times {{10}^{8}}}{400\times {{10}^{-9}}}=7.5\times {{10}^{14}}Hz \\\ & \\\ \end{aligned}$
Thus, by solving this equation we got frequency as, $7.5\times {{10}^{14}}Hz$

Note :
The electromagnetic spectrum encompasses the entire range of possible values for light, including wavelengths, frequencies, and energies. Most of us are familiar with visible light, which has a wavelength range of about 400 nm to 700 nm. Light can have much longer and shorter wavelengths than this, resulting in frequency and energy variations.