Everything Science Grade 12

10.2 CHAPTER 10. COLOUR

wavelength λ.

λ =

c

f

=

3 × 108

490 × 1012

= 6. 122 × 10 −7 m

= 612× 10 −^9 m

= 612 nm

Therefore the orange light has a wavelength of 612 nm.

Example 3: Frequency of Green

QUESTION

The wavelength of greenlight ranges between 500 nm an d 565 nm. Calculate

the range of frequenciesthat correspond to this range of wavelengths.

SOLUTION

Step 1 : Determine how to approach the problem

Use

c = f× λ

to determine f.

Step 2 : Calculate frequency corresponding to upper limit of wavelength

range

c = f× λ

f =

c

λ

=

3 × 108 m· s−^1

565 × 10 −^9 m

= 5, 31 × 1014 Hz

Step 3 : Calculate frequency corresponding to lower limit of wavelength

range