Final answer:
The energy of an electromagnetic wave can be calculated using the equation E = hc/λ, where E is the energy, h is Planck's constant (6.626 x 10^-34 J.s), c is the speed of light (3 x 10^8 m/s), and λ is the wavelength of the wave.
Step-by-step explanation:
The energy of an electromagnetic wave can be calculated using the equation E = hc/λ, where E is the energy, h is Planck's constant (6.626 x 10^-34 J.s), c is the speed of light (3 x 10^8 m/s), and λ is the wavelength of the wave.
In this case, the wavelength is given as 4.0 (units not specified), so we need to convert it to meters before plugging it into the equation.
Once the wavelength is in meters, you can substitute it into the equation to find the energy of the electromagnetic wave.