Embibe Experts Solutions for Chapter: Atomic Physics, Exercise 2: Exercise-2

If Bohr's theory is applicable to ${{}_{100}Fm}^{257}$ then radius of this atom in Bohr's unit is 

Figure shows the intensity-wavelength relations of $X$-rays coming from two different Coolidge tubes. The solid curve represents the relation for the tube $A$ in which the potential difference between the target and the filament is $V_A$ and the atomic number of the target material is $Z_A.$ These quantities are $V_B$ and $Z_B$ for the other tube. Then,

Wavelengths of $K_{a }$ lines of two elements are $250$ and $179 \mathrm{pm}$, respectively. Number of elements between these elements in the sequence will be

For soft $X$-rays the attenuation constant for aluminium is $1.73$ ${\mathrm{cm}}^{-1}.$ Then the percentage of $X$ -rays that will pass through an aluminium sheet of thickness $1.156 \mathrm{cm}$ will be

An $x$-ray tube, when operated at $50\mathrm{kV}$ tube voltage, records an anode current $20 \mathrm{mA}.$ If the efficiency of the tube for production of $x$-rays is $1\%$ then the heat produced per second in calories is nearly

Assertion: Neutrons penetrate matter more readily as compared to protons.

Reason: Neutrons are slightly more massive than protons.

Assertion : Bohr had to postulate that the electrons in stationary orbits around the nucleus do not radiate.

Reason : According to classical physics all moving electrons radiate.

Assertion: The hydrogen atom consists of only one electron, but its emission spectrum has many lines.

Reason: Only the Lyman series is found in the absorption spectrum of hydrogen atoms whereas in the emission spectrum all the series are found.