An X-ray tube is operated at `50 kV and 20 m A`. The target material of the tube has mass of `1 kg` and specific heat `495 J kg ^(-1) `^(@)C^(-1)`. One perent of applied electric power is converted into X-rays and the remaining energy goes into heating the target. Then,

Options

A. A suitable target material must have a low melting temperature
B. A suitable target material must have low thermal conductivity
C. The average rate of rise of temperature of target would be `4^(@) C//s`
D. The minimum wavelength of the `X` - rays emitted is about `0.25 xx 10^(-10) m`

Answer

D

Explanation

`P = VI = 50 xx 10^(5) xx 20 xx 10^(-3) = 1000 W`
power converted into heat ` = 990 W`
`ms Delta T - 990 rArr Delta T = 2 ^(@) C //sec`
Now `(hc)/(lambda_(min)) = eV rArr lambda_(min) = (hc)/(eV) = 0.248 xx 10^(-10) m`