A hydrogen atom initially in the ground level absorbs a photon, which excites it to the $n = 4$ level. Determine the wavelength and frequency of photon.
For ground level, $n_{1}=1$
Let $E_{1}$ be the energy of this level. It is known that $E_{1}$ is related with $n_{1}$ as
$E_{1}=\frac{-13.6}{n_{1}^{2}}\, e V$
$=\frac{-13.6}{1^{2}}=-13.6\, e V$
The atom is excited to a higher level, $n_{2}=4$
Let $E_{2}$ be the energy of this level.
$\therefore E_{2}=\frac{-13.6}{n_{2}^{2}} \,e V$
$=\frac{-13.6}{4^{2}}=-\frac{13.6}{16}\, e V$
The amount of energy absorbed by the photon is given as
$E=E_{2}-E_{1}$
$=\frac{-13.6}{16}-\left(-\frac{13.6}{1}\right)$
$=\frac{13.6 \times 15}{16} \,e V$
$=\frac{13.6 \times 15}{16} \times 1.6 \times 10^{-19}=2.04 \times 10^{-18} \,J$
For a photon of wavelength $\lambda,$ the expression of energy is written as
$E=\frac{h c}{\lambda}$
Where, $h=$ Planck's constant $=6.6 \times 10^{-34} \,Js$
$c=$ Speed of light $=3 \times 10^{8} \,m / s$
$\therefore \lambda=\frac{h c}{E}$
$=\frac{6.6 \times 10^{-34} \times 3 \times 10^{8}}{2.04 \times 10^{-18}}$
$=9.7 \times 10^{-8}\, m =97\, nm$
And, frequency of a photon is given by the relation, $v=\frac{c}{\lambda}$
$=\frac{3 \times 10^{8}}{9.7 \times 10^{-8}} \approx 3.1 \times 10^{15} \,Hz$
Hence, the wavelength of the photon is $97\, nm$ while the frequency is $3.1 \times 10^{15} \,Hz$.
One day on a spacecraft corresponds to $2$ days on the earth. The speed of the spacecraft relative to the earth is
Write characteristic of photon or How photon of electromagnetic radiation can be represented ?
Average force exerted on a non-reflecting surface at normal incidence is $2.4 \times 10^{-4} \mathrm{~N}$. If $360 \mathrm{~W} / \mathrm{cm}^2$ is the light energy flux during span of $1$ hour $30$ minutes. Then the area of the surface is:
A $160 \,W$ light source is radiating light of wavelength $6200 \,\mathring A$ uniformly in all directions. The photon flux at a distance of $1.8 \,m$ is of the order of .......... $m ^{-2} s ^{-1}$ (Planck's constant $\left.=6.63 \times 10^{-34} \,J - s \right)$
The number of photons emitted by a $10\,watt$ bulb in $10\,second,$ if wavelength of light is $1000\,\,\mathop A\limits^o ,$ is