Frequency, Wavelength, and Energy Calculations
SOLUTIONS

1.  Frequency of light is how many wave cycles occur per second.  At LC, we use f to represent frequency although in the textbook and often on websites, the greek symbol n ("nu") is used.

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2.  

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3.  c = f l

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4.    l = 425 nm               

f = ?  Hz

c = f l

c/l = f 

=   3.00 x 10¹⁷ nm/s  =  7.06 x 10¹⁴ sec^-1  =  7.06 x 10¹⁴ Hz
      425 nm

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5.  l = 295 nm   

f = ?  Hz

c = f l

c/l = f

f =  3.00 x 10¹⁷ nm/sec   =     1.02 x 10¹⁵  sec^-1 =  1.02 x 10¹⁵  Hz
       295 nm

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6.  l  =  3.19 cm

f = ?  Hz

c = f l

c/l = f

f = 3.00 x 10¹⁰ cm/sec =  9.40 x 10⁹  sec^-1 =  9.40 x 10⁹  Hz
     3.19 cm

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7.   f = 5.09 x 10¹⁴ Hz

l = ?  nm

c = f l

l = c / f

l  = 3.00 x 10⁸ m/sec   =   5.89 x 10^-7 m   *     10⁹  nm  =   5.89 x 10² nm
          5.09 x 10¹⁴  sec^-1                                       1 m

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8. 

f = 10 sec^-1

s = 5 km/sec

l = ?  km

We can make c (the speed of light) and s (speed) equivalent to each other.  c = f l

So,   s = f  l

l = s / f  =  5 km/sec  = 0.5 km
                    10 sec^-1

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9.  f = 5.09 x 10¹⁴ sec^-1

E = ?  J

E = h f

E = (6.63 x 10^-34  J sec)(5.09 x 10¹⁴ sec^-1)

E = 3.37 x 10^-19  J

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10.  f = 4.0 x 10¹⁴ sec^-1

E = ?  J

E = h f

E = h f = (6.63 x 10^-34  J sec)(4.0 x 10¹⁴ sec^-1)

E = 2.7 x 10^-19 J

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11. l = 550 nm 

f = ?  sec^-1

c = f l

c/l = f

f = 3.00 x 10¹⁷ nm/sec   =  5.5 x 10¹⁴ sec^-1
       550 nm

E = ?  J

E = h f

E = (6.63 x 10^-34  J sec)(5.5 x 10¹⁴ sec^-1)

E = 3.6 x 10^-19 J