Everything Science Grade 10

CHAPTER 11. ELECTROMAGNETIC RADIATION 11.2

Example 1: EM radiation I

QUESTION

Calculate the frequency of an electromagnetic wave with a wavelength of

4 , 2 × 10 −^7 m.

SOLUTION

Step 1:Wave equation

We use the formula:c=fλto calculate frequency. The speed of light

is a constant 3 × 108 m·s−^1.

Step 2:Calculate

c = fλ

3 × 108 m·s−^1 = f× 4 , 2 × 10 −^7 m

f = 7, 14 × 1014 Hz

Step 3:Quote the final answer

The frequency is 7 , 14 × 1014 Hz.

Example 2: EM Radiation II

QUESTION

An electromagnetic wave has a wavelength of 200 nm. What is the frequency of

the radiation?

SOLUTION

Step 1:What do we know?

Recall that all radiation travels at the speed of light (c) in vacuum. Since

the question does not specify through what type of material the wave is

Physics: Waves, Sound and Light 189