Question

X-rays of wavelength $0.140n-m$ are scattered from a block of carbon. What will be the wavelengths of X-rays scattered at ${90}^{\circ }$?

• A. $0.140n-m$
• B. $0.142n-m$
• C. $0.144n-m$
• D. $0.146n-m$

Answer 1

The correct option is B $0.142n-m$

Using Compton formula for scattering,

${\lambda }_f-{\lambda }_i=\frac{h}{m_{e}c}(1-cos\theta )$

Here, $\theta ={90}^0⟹cos\theta =0$

So, ${\lambda }_f=0.14n-m+\frac{6.6\times {10}^{-34}}{9.1\times {10}^{-31}\times 3\times {10}^8}=0.14n-m+0.0024n-m=0.142n-m$

Option B is correct.