Lights from a red laser pointer has a speed of 3.0 x 10^8 m/s and has a wavelenght of 6.5 x 10^-7 m. what is the frequency of this light

You have  

1

s

, and oftentimes with wavelength, you want to convert to  

nm

which is UV-Vis range (

200~700 nm

), and is often of spectral interest.

What you want to do is:

1

s

→

1

m

→

m

→

nm

Conversion factors are extremely useful, and one easy one to remember is the speed of light, which is about  

3

×

10

8

m/s

.

1

1

s

⋅

s

m

=

m

And finally, we can convert to  

nm

:

10

9

nm

=

1 m

→

conversion factor:  

10

9

nm

1 m

m

⋅

10

9

nm

1

m

Thus, overall, you just have:

nm

=

1

1

s

⋅

s

3

×

10

8

m

⋅

10

9

nm

1

m

=

1

1

/

s

⋅

3

×

10

8

m

/

s

×

10

9

nm

1

m

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