Question

Calculate the quantum of energy in (a) yellow light wavelength 6×10^_7 m (b) X rays of wavelength 5×10^10m

Answer 1

 The quantum of energy is $E=h\nu$ where $\nu=\frac{c}{\lambda}$ and $h=6.6⋅10^{−34}J·s$ .

(a) For yellow light $\lambda_y=6\cdot 10^{-7}m$ and $\nu_y=\frac{3\cdot10^8ms^{-1}}{6\cdot10^{-7}m}=5\cdot10^{14}Hz$.

Quantum energy is $E_y=6.6\cdot 10^{-34}\cdot 5\cdot 10^{14}J=3.3\cdot 10^{-19}J$

(b) For X-ray we have $\lambda_x=5\cdot 10^{-10}m$ , $\nu_x=\frac{3\cdot10^8ms^{-1}}{5\cdot10^{-10}m}=6\cdot10^{17}Hz$ and

$E_x=6.6\cdot 10^{-34}\cdot 6\cdot 10^{17}J=3.96\cdot 10^{-16}J$

Answer:  the quantum of energy in (a) yellow light is $3.3\cdot 10^{-19}J$ (b) X rays is $3.96\cdot 10^{-16}J$