3.4 Electromagnetic Spectrum

Pre-Lecture Reading 3.4

•
See Types of Light.
•
Visible light—the light that we can see with our eyes—is only a tiny sliver of the entire electromagnetic spectrum, with wavelengths between ≈700 nm (red) and ≈400 nm (violet).

Figure 1: Image Credit: Advanced Light Source, Lawrence Berkeley National Laboratory

E ∝ ν

λ × ν = v

( 6 )

E = hν

Example:
If you double a light wave's frequency, you double its energy.

( 7 )

λ × ν = c

( 8 )

λ =

( 9 )

ν =

Example:
Consider a 1-m radio wave. Hence,

λ = 1 m

and

ν =

(3 × 10⁸ m/s)

(1 m)

= 3 × 10⁸ s⁻¹ = 3 × 10⁸ Hz.

Example:
Consider a 10⁸-Hz radio wave. Hence,

ν = 10⁸ Hz

and

λ =

(3 × 10⁸ m/s)

(10⁸ Hz)

= 3 m.

For λ measured in nm, µm, mm, cm, m, and km, the following values of c, respectively, can be used to simplify calculations: