Question

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

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

Answer 1

Answer: (A)

$\Rightarrow$ $Frequency=\frac{velocityoflight(c)}{wavelength(\lambda )}$ Given, frequency
$=8\times {10}^{15}{s}^{-1}$ velocity of light
$=3.0\times {10}^{8}m{s}^{-1}$
$\therefore$ $8\times {10}^{15}=\frac{3\times {10}^8}{\lambda }$ or $\lambda =\frac{3\times {10}^8}{8\times {10}^{15}}=0.375\times {10}^{-7}m$
$=3.75\times {10}^{1}nm$ $\approx 40nm$