Question

Helppp me please !!

Answer 1

Answer:

the frequency of this light is $1.5\,\,10^{16}$ Hz (which coincides with the fourth option listed among possible answers)

Explanation:

Recall the relationship between wavelength and frequency of radiation based upon the speed of light in vacuum:

$frequency\,*\,wavelength\,=\, speed\,\,of\,light\\frequency\,*\,wavelength\,=\,3\,\,10^8\,\frac{m}{s} \\frequency\,*\,20 \,\,10^{-9}\,m\,=\,3\,\,10^8\,\frac{m}{s}\\frequency\, =\,\frac{3\,\,10^8}{2\,\,10^{-9}} \,\frac{1}{s} \\frequency\,=1.5\,\,10^{16}\,\,Hz$

In the process shown above, we have written the speed of light in meters per second, and also converted the 20 nano-meters into meters, in order to reduce SI units properly and have the result shown in units of 1/second (that is hertz's - abbreviate "Hz")