Abeam of light has a wavelength of 4.5 × 10^−7
meter in a vacuum. the frequency of this light is
(1) 1.5 × 10^−15 hz (3) 1.4 × 10^2 hz
(2) 4.5 × 10^−7 hz (4) 6.7 × 10^14 hz

Wavelength formula is C=λf or λ=C/f or f = C/λ, so Frequency = Velocity divided by wavelength, where C is the velocity, which is the speed of light: 3.00×108 m/sec

λ is the wavelength in meters
f is the frequency in Hertz (cycles per second)
f=3.00×108msec/4.5x10−7m=6.7x1014Hz

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