Question

An X-ray tube is operating at $50kV$ and $20mA$. The target material of the tube has mass of $1kg$ and specific heat $495Jk{g}^{-1\circ }{C}^{-1}$. One percent of applied electric power is converted into X-rays and the remaining energy goes into heating the target. Then

• A. A suitable target material must have high melting temperature
• B. A suitable target material must have low thermal conductivity
• C. The average rate of rise of temperature of the target would be $2^{\circ }C{s}^{-1}$
• D. The minimum wavelength of X-rays emitted is about $0.25\times {10}^{-10}m$

Answer 1

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

The correct options are
A A suitable target material must have high melting temperature
C The average rate of rise of temperature of the target would be $2^{\circ }C{s}^{-1}$
D The minimum wavelength of X-rays emitted is about $0.25\times {10}^{-10}m$

We know that,

$P=VI=50\times {10}^3\times 20\times {10}^{-3}$

$P=1000W$

$MS\Delta T=990\Rightarrow \Delta T=2^{0}c/sec$

Power converted into heat $=990W$

Now $\Rightarrow \frac{hc}{{\lambda }_{min}}=eV$

$\Rightarrow {\lambda }_{min}=\frac{hc}{eV}$

$\underset{–}{{\lambda }_{min}=0.248\times {10}^{-10}m}$