A radioactive source emits X—rays of very short wavelength (10 -13m ) what is the frequently of these rays?
A. 2 à— 10
18HZ
B. 3 × 10
19HZ
C. 3 à— 10
21HZ
D. 3 à— 10
-19HZ
Correct Answer: C
Explanation
\(Wavelength (\lambda) = 10^{-13}m\)
Speed of X-ray = speed of light \(C = 3×10^{8}m/s\)
Frequently (f) = ?
\(Using V = f\lambda (or (– f π for electromagnetic wave)\)
\(f = \frac{c}{\lambda} = 3 \times 10^{8} ÷ 10^{-13} = 3 \times 10^{8} \times 10^{13}\)
= \(3 \times 10^{8} \times 10^{13}\)
= \(3 \times 10^{21}Hz\)
