Question

The value of Planck's constant is $ 6.63 \times 10^{-34} \,Js.$ The velocity of light is $3.0 \times 10^8\, ms^{-1}$. Which value is closest to the wavelength in nanometers of a quantum of light with frequency of $8 \times 10^{15}\, s^{-1}$?

• A. $4 \times 10^1$
• B. $3 \times 10^7$
• C. $2 \times 10^{25}$
• D. $5 \times 10^{-18}$

Answer 1

Answer: (A)

Frequency (v)$=\frac{c}{\lambda}=\frac{3\times10^8 m\, s^{-1}}{8\times 10^{15}s^{-1}}$
$ = 0.375\times10^{-7}\, m$
$ = 3.75 \times 10^1 nm \approx4 \times 10^1\, nm$