# Given below are some famous numbers associated with electromagnetic radiations in different contexts in physics. Which of the following belongs to radio waves?

$\begin {array} {1 1} (a) 5890\: A^{\circ} – 5896\: A^{\circ} & \quad (b)\;2.7\: K \\ (c)\;1057\: MHz & \quad (d)\;14.4\: keV \end {array}$

## 1 Answer

$(5890 – 5896)A^{\circ}$ is the yellow light of the visible spectrum
Temperature, $T = 2.7 K then \: \lambda_m = \large\frac{0.29}{T}$$= \large\frac{0.29}{2.7}$$ = 0.11 cm$
$1057\: MHz$ belongs to the short wavelength end of radio waves
Energy, $E = \nu h$
$\Rightarrow \nu= \large\frac{E}{h}$
$=\large\frac{ 14.4 \times 10^3 \times 1.6 \times 10^{-19}}{ (6.6 \times 10^{-34} )}$$= 3.4 \times 10^{18 } \: Hz$
This corresponds to the X-rays
Ans :hence (c) is the correct answer

answered Mar 3, 2014
edited Oct 8, 2014

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