Question

Choose the right statement from the following-

• A. In an X ray tube, if the accelerating voltage is 30 KV, the cutoff wavelength, in one significant digit, will be $0.4\stackrel{\circ }{A}$
• B. In photoelectric effect experiment, if the wavelength of the incident photon is 500 nm, electrons will be ejected out of a metal having work function 3 eV.
• C. According to the Bohr’s theory, the speed of the electron in II excited state is $\frac{V_0}{3}$, where $V_0$ is the speed of the electron in the ground state.
• D. A beam of photons emitted by the excited H atoms is passed through a prism and then, allowed to fall on a screen. Only Balmer series will be seen on the screen by a student who is performing the experiment

Answer 1

Answer: (A), (C), (D)

A beam of photons emitted by the excited H atoms is passed through a prism and then, allowed to fall on a screen. Only Balmer series will be seen on the screen by a student who is performing the experiment

$\left(A\right)e{V}_0=\frac{hc}{{\lambda }_{min}},{\lambda }_{min}.=\frac{12400}{30000}=0.4A^{\circ }$
(B)Energy of photon
$=\frac{12400}{5000}=2.48eV<\varphi$
Hence electrons will not eject.
(C) In hydrogen atom, speed $V\propto \frac{1}{n}$
Here, in ground state n = 1 and in second excited state n = 3.
$\frac{V_3}{V_0}=\frac{1}{3}\Rightarrow V_3=\frac{V_0}{3}$
(D) When the emitted light is passed through a prism, only a few narrow lines, called a line spectrum, which is a spectrum in which light of only a certain wavelength is emitted or absorbed, rather than a continuous range of wavelengths. The light emitted by hydrogen atoms is red because, of its four characteristic lines, the most intense line in its spectrum is in the red portion of the visible spectrum, at 656 nm.