Question

The value of Planck's constant $(h)$ 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 meters) of a quantum of light with frequency of $8 \times 10^{15} s ^{-1}$ ?

• A. $5\times10^{-18}$
• B. $3.75 \times 10^{-8}$
• C. $3\times10^{7}$
• D. $2\times10^{-25}$

Answer 1

Answer: (B)

Given
Planck's constant $=6.63 \times 10^{-34} Js$
Speed of the light $=3 \times 10^{8} nms ^{-1}$
Frequency of quanta $=8 \times 10^{15} s ^{-1}$
We know that
$v =\frac{ c }{\lambda}$
$v =\frac{3 \times 10^{8}}{8 \times 10^{+15}}=\frac{3}{8} \times 10^{-7}$
$=3.75 \times 10^{-8}$